Guarav,
We have solved this to a certain extent with custom development.
1. The Client PLU has to be sent to the POS
2. Once a store credit is invoked as a method of payment, POS asks for a client number
3. The POS sends a message containing transaction total along with client number to ERP regarding the client's balance via incoming FTP flat file.
4. The ERP sends a message back via FTP flat file confirming to proceed transaction if remaining credit is available, and to reject if credit is not available.
5. When the transaction is completed, the transaction is sent in the TLOG file with customer number.
Let me know if this helps.
Regards,
Jose