Transaction code while processing message using Proxy

Hi,

I am processing a message inbound into R3 using a proxy and using a BAPI to post a FI document.

However the FI substitutions and validations in R3 are based of transaction code sy-tcode. The substitutions have a check "if SY_TCODE = 'FB01'.

Processing a Proxy does not seem to have a TCODE. I added code within the processing to export sy-tcode to INDX within the proxy processing and it returned nothing.

I have set the TCODE for the FI transaction in the BADI but this does not help.

Any information that will help me is greatly appreciated.