Hi Varun,
You can approach it in 2 ways:
1. From Module pool, fill the BDC_DATA table and CALL TRANSACTION for every click on the create button OR
2. On CREATE button click, keep filling your internal table with the values and at the end of selection Event you can create a session with all those entries to run the BDC in background.
For 2nd method : make sure that the customer reference taken is not the one which was jus created in the same execution.
Hope it helps!
Regards,
Akhila Bidare