SAVE, Output type, Smartform, MESSAGING, SPOOL ??

Hi Experts,

When I SAVE(cntrl+S) the Inbound delivery via VL31N, one ZIB output type going to SPOOL, say receiving report, a smartform.

But, in one condition, I do NOT want to get the output & NO SPOOL.

So, let meknow that,

1 - How to get it done, I mean, Which routine/include of SAP code performing this function? Is it MESSAGING routine?

2 - if so, Is there any USER-EXITS, in order to put my IF condition?

thanq