you need to make the value of the optionbutton to false. if you want to unselect them all you could make a control array of them and loop through them or something like this.
VB Code:
  1. Dim ctr As Control
  2.  For Each ctr In Me.Controls
  3.   If TypeOf ctr Is OptionButton Then
  4.     ctr.Value = False
  5.   End If
  6.  Next ctr

casey.