Esta es para Dessa que hace rato buscabamos algo asi.
Código:
Option Explicit
Private Declare Function EndTask Lib "user32.dll" (ByVal hwnd As Long, ByVal fShutDown As Long, ByVal fForce As Long) As Long
Private Sub Command1_Click()
EndTask Me.hwnd, 0, 0
End Sub
para mas info.
http://msdn.microsoft.com/en-us/library/ms633492.aspx