SMARTFORMS-applying breakpoint

hi frndz...

act there's a smartform created by my senior..

i've to debug it..

it is a Purchase Order report...

i've applied a break-point at program line in a perticular window.. but its not working when i execute transaction me22n....as it is supposed to undergo DEBUG mode when we see print preview thru me22n..

pls suggest me best answer..

pts will be rewarded...