So, you want to find all repeaters on a page, find all the controls for each repeaterItem, and then do something depending on the controls type?
This is my untested unverified thought pattern..
Perhaps you can do something along the lines of..
For Each c as Control In Me.Controls
Dim rpt as Repeater = TryCast(c, Repeater)
If rpt IsNot Nothing Then
For Each item as RepeaterItem In rpt.Items
For Each rptC As Control In item.Controls
Select Case GetType(rptC)
Case GetType(New TextBox())