Running report online or batch

Hi Experts,

I am doing some validations in a report program based on sy-batch paramter when the report is run in background.

I have made this check i.e to find out if sy-batch is X or not in "AT SELECTION SCREEN" event.

I wanted to know if this is ok or should i check it  in initialization ? As of now in my unit testing its working fine.

But just wanted to know if this check can fail anywhere if we do it in at selection screen event and not initialization.