Private Sub Form_MouseDown(Button As Integer,Shift As Integer,X As Single, Y As Single)
If Button = 1 Then ' acLeftButton
MsgBox "You pressed the left button."
ElseIf Button = 2 Then 'acRightButton
MsgBox "You pressed the right button."
ElseIf Button = 4 Then 'acMiddleButton
MsgBox "You pressed the middle button."
End If
End Sub