Mike,

The problem is not with the SYS(1270) command, but rather when and where you check it. It is much easier and less prone to problems to use the Cancel property of the command button and then chekc for the Escape key having been pressed.

IOW, if the situation is bypassing teh valid test of a contrl if Cancel was clicked then simply maknig the Cancel property for that button .T. and doing this at the start of teh Valid is fine;

* Valid
IF LastKey() = 27
   RETURN && valid is passed
ENDIF
* Other valid code here

If it is allowing a process to be interrupted by the cancel button then you need to process events at regular intervals during the process.

* Some lengthy process
LOCAL lnCntr
lnCntr = 1
DO WHILE ...
   Blah
   Blah
   Blah
   lnCntr = lnCntr + 1
   IF MOD(lnCntr,100) = 0
      DoEvents
      IF LastKey() = 27
         Exit
      ENDIF
   ENDIF
ENDDO