(If you don't want to use API) Use the MouseUp event instead of Click event.
vb Code:
  1. Private Sub Command1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
  2.    Dim CtrlDown As Integer
  3.    
  4.    CtrlDown = Shift And 7
  5.    
  6.    If CtrlDown = vbCtrlMask Then 'control key pressed
  7.         MsgBox "Show HIDDEN form"
  8.    Else
  9.         MsgBox "Show regular form"
  10.    End If
  11.    
  12. End Sub
Reference:
http://msdn2.microsoft.com/en-us/lib...30(VS.60).aspx
http://msdn2.microsoft.com/en-us/lib...14(VS.60).aspx