call function '' in update task - code inside is BDC

hi to all,

in using call function '' in update task

the code inside is bdc. is this possible?

my scenario is from VA01 then post billing to VF01,

i am using user-exit MV45AFZZ in subroutine userexit_save_document.

i need to post billing after va01 save.

thanks to all.