How differentiate different data in smartform with foreground and hinterground mode

Hallo Experts,

I have question reagrd smartform in foreground  and hinterground mode. When i want a generate form in foreground then print data in smartform in z.b Contact : SY-USNAME. ( hardcord) . Loging User

When a generate formular  in hinterground then data " Contact " print from z-table instead SY-USNAME in smartform. In Z-table i have another user. I have this requirement. How is it possible that when generate formular  in hintergorund print data from Z-table instead SY-UNAME.

Please give me idea or suggest some code.

This is my code

CALL FUNCTION gv_fm_name

     EXPORTING

       control_parameters   = im_control_para

       output_options       = im_output_opt

       iv_user              = sy-user  ( Loging User )

     IMPORTING

       job_output_info      = is_output_info

     TABLES

       lt_vbap              = it_data

     EXCEPTIONS

       formatting_error     = 1

       internal_error       = 2

       send_error           = 3

       user_canceled        = 4

       OTHERS               = 5.

Thanks