Hello, I am very new to this whole vb universe. But I am trying to make a program for my teacher to use to calculate the amount of hours a student has been signed in each day.

The goal of the program is to find the time between two textbox values (hh:mm) and add the answer into another textbox.
This is how how I have done that:

Code:
        Dim time1 As Date
        Dim time2 As Date
        Dim span1 As TimeSpan
        time1 = Convert.ToDateTime(TextBox1.Text)
        time2 = Convert.ToDateTime(TextBox2.Text)
        span1 = time2.Subtract(time1)
        Label5.Text = span1.ToString("hh\:mm")
The timespan between the two datetimes is then added to a master list of times so they can all be later added to create a total.
This is my entire project so far and I'm hoping you guys here can tell me how to properly add the time spans in the masterlist. Currently this will work but will return "12:00" in label42 and I don't know why. Just ask if I need to further elaborate on this. Here is my code:

Code:
Public Class Form1


    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Label5.Text = ""
        Label42.Text = ""
        Label43.Text = ""
    End Sub


    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        TextBox1.Text = ""
        TextBox2.Text = ""
        Label5.Text = ""
    End Sub


    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim time1 As Date
        Dim time2 As Date
        Dim span1 As TimeSpan
        time1 = Convert.ToDateTime(TextBox1.Text)
        time2 = Convert.ToDateTime(TextBox2.Text)
        span1 = time2.Subtract(time1)
        Label5.Text = span1.ToString("hh\:mm")


        If CheckBox1.Checked Then
            If TextBox4.Text = "" And TextBox3.Text = "" Then
                TextBox4.Text = TextBox1.Text
                TextBox3.Text = TextBox2.Text
                TextBox5.Text = span1.ToString("hh\:mm")
            ElseIf TextBox7.Text = "" And TextBox8.Text = "" Then
                TextBox7.Text = TextBox1.Text
                TextBox8.Text = TextBox2.Text
                TextBox6.Text = span1.ToString("hh\:mm")
            ElseIf TextBox10.Text = "" And TextBox11.Text = "" Then
                TextBox10.Text = TextBox1.Text
                TextBox11.Text = TextBox2.Text
                TextBox9.Text = span1.ToString("hh\:mm")
            ElseIf TextBox19.Text = "" And TextBox20.Text = "" Then
                TextBox19.Text = TextBox1.Text
                TextBox20.Text = TextBox2.Text
                TextBox18.Text = span1.ToString("hh\:mm")
            ElseIf TextBox16.Text = "" And TextBox17.Text = "" Then
                TextBox16.Text = TextBox1.Text
                TextBox17.Text = TextBox2.Text
                TextBox15.Text = span1.ToString("hh\:mm")
            ElseIf TextBox13.Text = "" And TextBox14.Text = "" Then
                TextBox13.Text = TextBox1.Text
                TextBox14.Text = TextBox2.Text
                TextBox12.Text = span1.ToString("hh\:mm")
            ElseIf TextBox28.Text = "" And TextBox29.Text = "" Then
                TextBox28.Text = TextBox1.Text
                TextBox29.Text = TextBox2.Text
                TextBox27.Text = span1.ToString("hh\:mm")
            ElseIf TextBox25.Text = "" And TextBox26.Text = "" Then
                TextBox25.Text = TextBox1.Text
                TextBox26.Text = TextBox2.Text
                TextBox24.Text = span1.ToString("hh\:mm")
            ElseIf TextBox22.Text = "" And TextBox23.Text = "" Then
                TextBox22.Text = TextBox1.Text
                TextBox23.Text = TextBox2.Text
                TextBox21.Text = span1.ToString("hh\:mm")
            ElseIf TextBox37.Text = "" And TextBox38.Text = "" Then
                TextBox37.Text = TextBox1.Text
                TextBox38.Text = TextBox2.Text
                TextBox36.Text = span1.ToString("hh\:mm")
            ElseIf TextBox34.Text = "" And TextBox35.Text = "" Then
                TextBox34.Text = TextBox1.Text
                TextBox35.Text = TextBox2.Text
                TextBox33.Text = span1.ToString("hh\:mm")
            ElseIf TextBox31.Text = "" And TextBox32.Text = "" Then
                TextBox31.Text = TextBox1.Text
                TextBox32.Text = TextBox2.Text
                TextBox30.Text = span1.ToString("hh\:mm")
            ElseIf TextBox46.Text = "" And TextBox47.Text = "" Then
                TextBox46.Text = TextBox1.Text
                TextBox47.Text = TextBox2.Text
                TextBox45.Text = span1.ToString("hh\:mm")
            ElseIf TextBox43.Text = "" And TextBox44.Text = "" Then
                TextBox43.Text = TextBox1.Text
                TextBox44.Text = TextBox2.Text
                TextBox42.Text = span1.ToString("hh\:mm")
            ElseIf TextBox40.Text = "" And TextBox41.Text = "" Then
                TextBox40.Text = TextBox1.Text
                TextBox41.Text = TextBox2.Text
                TextBox39.Text = span1.ToString("hh\:mm")
            Else : MessageBox.Show("Clear the totals list to continue calculatimg")
            End If
        End If


    End Sub


    Private Sub Label1_Click(sender As System.Object, e As System.EventArgs) Handles Label1.Click
        MessageBox.Show("Time Sheet Calculator" & vbCrLf & "Version: 1.0.0" & vbCrLf & "Created by: Gary Byrne")
    End Sub


    Private Sub Button3_Click(sender As System.Object, e As System.EventArgs) Handles Button3.Click
        TextBox3.Text = ""
        TextBox4.Text = ""
        TextBox5.Text = ""
        TextBox6.Text = ""
        TextBox7.Text = ""
        TextBox8.Text = ""
        TextBox9.Text = ""
        TextBox10.Text = ""
        TextBox11.Text = ""
        TextBox12.Text = ""
        TextBox13.Text = ""
        TextBox14.Text = ""
        TextBox15.Text = ""
        TextBox16.Text = ""
        TextBox17.Text = ""
        TextBox18.Text = ""
        TextBox19.Text = ""
        TextBox20.Text = ""
        TextBox21.Text = ""
        TextBox22.Text = ""
        TextBox23.Text = ""
        TextBox24.Text = ""
        TextBox25.Text = ""
        TextBox26.Text = ""
        TextBox27.Text = ""
        TextBox28.Text = ""
        TextBox29.Text = ""
        TextBox30.Text = ""
        TextBox31.Text = ""
        TextBox32.Text = ""
        TextBox33.Text = ""
        TextBox34.Text = ""
        TextBox35.Text = ""
        TextBox36.Text = ""
        TextBox37.Text = ""
        TextBox38.Text = ""
        TextBox39.Text = ""
        TextBox40.Text = ""
        TextBox41.Text = ""
        TextBox42.Text = ""
        TextBox43.Text = ""
        TextBox44.Text = ""
        TextBox45.Text = ""
        TextBox46.Text = ""
        TextBox47.Text = ""
    End Sub


    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
        Dim total1 As Date
        Dim total2 As Date
        Dim total3 As Date
        Dim total4 As Date
        Dim total5 As Date
        Dim total6 As Date
        Dim total7 As Date
        Dim total8 As Date
        Dim total9 As Date
        Dim total10 As Date
        Dim total11 As Date
        Dim total12 As Date
        Dim total13 As Date
        Dim total14 As Date
        Dim total15 As Date
        Dim tstotal As Date


        If TextBox5.Text = "" Then
        Else
            total1 = Convert.ToDateTime(TextBox5.Text)
        End If
        If TextBox6.Text = "" Then
        Else
            total2 = Convert.ToDateTime(TextBox6.Text)
        End If
        If TextBox9.Text = "" Then
        Else
            total3 = Convert.ToDateTime(TextBox9.Text)
        End If
        If TextBox18.Text = "" Then
        Else
            total4 = Convert.ToDateTime(TextBox18.Text)
        End If
        If TextBox15.Text = "" Then
        Else
            total5 = Convert.ToDateTime(TextBox15.Text)
        End If
        If TextBox12.Text = "" Then
        Else
            total6 = Convert.ToDateTime(TextBox12.Text)
        End If
        If TextBox27.Text = "" Then
        Else
            total7 = Convert.ToDateTime(TextBox27.Text)
        End If
        If TextBox24.Text = "" Then
        Else
            total8 = Convert.ToDateTime(TextBox24.Text)
        End If
        If TextBox21.Text = "" Then
        Else
            total9 = Convert.ToDateTime(TextBox21.Text)
        End If
        If TextBox36.Text = "" Then
        Else
            total10 = Convert.ToDateTime(TextBox36.Text)
        End If
        If TextBox33.Text = "" Then
        Else
            total11 = Convert.ToDateTime(TextBox33.Text)
        End If
        If TextBox30.Text = "" Then
        Else
            total12 = Convert.ToDateTime(TextBox30.Text)
        End If
        If TextBox45.Text = "" Then
        Else
            total13 = Convert.ToDateTime(TextBox45.Text)
        End If
        If TextBox42.Text = "" Then
        Else
            total14 = Convert.ToDateTime(TextBox42.Text)
        End If
        If TextBox39.Text = "" Then
        Else
            total15 = Convert.ToDateTime(TextBox39.Text)
        End If


        'this is where i want to add all the totals (total1 through total15)
        tstotal = Date.FromOADate(Val(total1) + Val(total2))
        Label42.Text = tstotal.ToString("hh\:mm")


    End Sub
End Class
Also if anyone could tell me how to clean up my code it would be greatly appreciated. I'm eager to learn