Problem in Undo event

Guys how to code the undo event in subform..

ex:
My main form is LockerEdit
Subform of LockerEdit form is LockEmpStatus
Sub form of LockEmpStatus form is QLockerOccupants

Now my cancel button is in the QLockerOccupants form so i need to cancel the data located in the LockEmpStatus form. How i can do that? I tried already the Docmd****nCommand acCmdUndo and Me.Undo but it doesn't work..

Any reply would be much appreciated.
Tnx in advance.God Bless...