Hi.

I'm not exactly sure HOW to do it, but I believe you could use the WndProc method of the form and check for WM_NCMBUTTONDOWN and WM_NCMBUTTONUP messages.

Something like this maybe...
VB Code:
  1. Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
  2.     If m.Msg = WM_NCMBUTTONDOWN Then
  3.                   'User clicked the caption or one of the edges
  4.                   'Block Imagesizing here
  5.     ElseIf m.Msg = WM_NCMBUTTONUP Then
  6.                   'User released the caption or one of the edges
  7.                   'Perform resize here if size has changed
  8.     End If
  9.  
  10.     MyBase.WndProc(m)
  11. End Sub

I hope this is of any help...