another way is to create your own factory at the cnt object level to restrict the where and overwrite the factory in the lookup field.
<PDM_MACRO name=dtlLookup hdr="Assignee" attr=assignee evt="onBlur=\\\"detailSyncEditForms(this)\\\""
FACTORY cst {
RESTRICT "type = 2305" { type = 2305} ;
DOMSET cst_list "combo_name,phone_number,contact_num,organization,location" "" DYNAMIC;
STANDARD_LISTS {
SORT_BY "combo_name,phone_number,contact_num,organization=organization.name,location=location.name";
WHERE "delete_flag = 0" ;
MLIST OFF ;
RLIST OFF ;
};
REL_ATTR id ;
COMMON_NAME combo_name ;
FUNCTION_GROUP "contact" ;
} ;