hi,
try this
Dim grdM As GridView = DirectCast(repeaterView1.FindControl("MasterGrid"), GridView)
For Each rowM As GridViewRow In grdM .Rows
Dim grdC As GridView = DirectCast(rowM .Cells(0).FindControl("ChildGrid"), GridView)
For Each rowC As GridViewRow In grdC .Rows
Dim lnkPurchase As LinkButton = DirectCast(rowC.FindControl("lnkPurchase "), LinkButton)
Next
Next