VB Code:
  1. Option Explicit

  2. Private closedByApp As Boolean

  3.  
  4.  
  5. Private Sub Command1_Click()

  6.     closedByApp = True

  7.     Unload Me

  8. End Sub

  9.  
  10. Private Sub Form_Unload(Cancel As Integer)

  11.     If Not closedByApp Then MsgBox "Someone clicked the x !"

  12. End Sub