Hi Prameet,
FB03 is belongs to package FIDC. There are no user exits available for FIDC package.
You can findout list of BADIs being called in the FB03 transaction by keeping the breakpoint in GET_INSTANCE, GET_CLASS_NAME_BY_INTERFACE & GET_INSTANCE_FOR_SUBSCREENS methods of class CL_EXITHANDLER.
Thanks & Regards,
Venugopal M N