Hi Pranav,
The problem is not clear. Is it that the VPRS condition on the billing document does not match the COGS posted in FI during GI ? In that case notes 372772 and 1365939 would be useful.
Or is it that you want the GI to be posted to COPA ? In that case please refer my WIKI
http://wiki.sdn.sap.com/wiki/x/XIOeDg
regards
Waman