workflow for MRIS

HI all ,

i am doing a workflow for " notify planned invoice expiry date "

when i run mris on a purchease order.

when i see the billing status for the invoice generated in me23n it shows status "C".(completely processed)

but when i check the table FPLT for field FKSAF it shows status "A". I need to send notification on the expiry of notification and i am checking this table for it .

Please suggest where else can i find the billing status.

Points will be rewarded for every possible help provided.

Thanx

aditya