Ops piccolo esempio grezzo grezzo:

codice:
 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        DirectCast(FindControl("TextBox1"), TextBox).Text = "Find it"
    End Sub

    Function FindControl(ByVal name As String) As Control
        For Each ctr As Control In Me.Controls
            If ctr.Name = name Then
                Return ctr
            End If
        Next
    End Function