Ahh then you have to cast it to a combobox specifically:

VB Code:
  1. Dim ComBox As Control
  2.         For Each ComBox In Me.Controls
  3.             If TypeOf ComBox Is ComboBox Then
  4.                 Try
  5.                     'if not bound
  6.                     ComBox.Text = ""
  7.                     'if bound
  8.                     DirectCast(ComBox, ComboBox).SelectedIndex = -1
  9.                 Catch
  10.                 End Try
  11.             End If
  12.         Next