Trouble Enabling/Disabling TextBoxes

Good morning ASP programmers,

I am trying to write a CodeBehind subroutine that will iterate through a form's controls and Enable or Disable all the form's TextBoxes.  Here is what I have attempted:
1 Private Sub EnableInput(ByVal EInput As Boolean)
2 'This subroutine enables/disables all the Form's textboxes.
3 Dim ctl As Control
4 Dim tb As TextBox
5
6 ' Attempt #1
7 'For Each tb In Me.Controls
8 ' tb.Enabled = EInput
9 'Next
10
11 ...