Substituting BSEG-ZUONR value in MIRO with PO details.

Hi All,

I need to substitute the value of the assignment field (BSEG-ZUONR) with ebeln and ebelp details. I have coded a substitution exit

at call point 2 in FI at item level. When i debug and check my code BSEG document no has no values(actually it is $ 1) and ebelp and ebeln values are blank. Does any have an idea how to get the values for PO order no and item no.

I am using transaction MIRO. The sort key 010 and this requrement is for document type RE.

Regards,

Vanita.