Hi Andie.
you can get the partner by using 'CRM_GPM_BUPAP_HELP' this function module.
This is the sample code try this..
DATA:
ls_map TYPE if_bsp_wd_valuehelp_f4descr=>gtype_param_mapping,
lt_inmap TYPE if_bsp_wd_valuehelp_f4descr=>gtype_param_mapping_tab,
lt_outmap TYPE if_bsp_wd_valuehelp_f4descr=>gtype_param_mapping_tab.
ls_map-context_attr = 'your field name'. " Field from where F4 help was triggered and selection needs to come back
ls_map-f4_attr = 'PARTNER'. " Field in the search help
APPEND ls_map TO: lt_inmap,lt_outmap.
CREATE OBJECT rv_valuehelp_descriptor TYPE cl_bsp_wd_valuehelp_f4descr
EXPORTING
iv_help_id = 'CRM_GPM_BUPAP_HELP'
iv_help_id_kind = if_bsp_wd_valuehelp_f4descr=>help_id_kind_name
iv_input_mapping = lt_inmap
iv_output_mapping = lt_outmap
iv_trigger_submit = abap_true.
Thanks & Regards,
Srinivas.