On Error GoTo Err_btnUndo_Click
'undo record
D_DI = "CA"
try something like this on your button
DoCmd.DoMenuItem Ac_FORMBAR, Ac_EDITMENU, Ac_UNDOFIELD, , Ac_MENU_VER20
'goto previous record
DoCmd.GoToRecord , , Ac_PREVIOUS
Exit_btnUndo_Click:
Exit Sub
Err_btnUndo_Click:
MsgBox Error$
Resume Exit_btnUndo_Click