Stop and exit subroutine process without saving data, back to standard screen.

Hi,

Currently i am triggering a user exit in PM module.

Would like to stop it like how error message work by preventing the progress from Stage A to Stage B.

Question is what syntax in ABAP will allow the user exit to trigger the stop behavior and back to the main screen without saving any data?

I tried Exit & leave, somehow it stop, but still continue to save screen data, or it just leave the standard program.

Please help.

Thanks.