Changing sender id for mail from vf03

Hi Experts,

When I send a billing document from VF03 to a customer, the e-mail address is read from my sap user (SU01). I would like an e-mail address for each billing type, but I don't now how to change "mail_sender" parameters in the smartforms (ZRLB_INVOICE program).

Can you help me, please?

sharing piece of code , where i think could make a difference ,

PERFORM set_print_param USING    ls_addr_key

                                      ls_dlv-land

                             CHANGING ls_control_param

                                      ls_composer_param

                                      ls_recipient

                                      ls_sender

                                      cf_retcode

here the sender is is_sender : DATA: ls_sender             TYPE swotobjid.

swotobjid - structure contains

LOGSYS

OBJTYPE

OBJKEY

DESCRIBE

i dunno how it has 2 b changed. right now i guess it's getting filled with user name data from su01.

Thanks.

Arun