Hi,
you can use update_object_super
uuid who;
send_wait(0,top_object(), "call_attr", "cnt", "current_user_id");
who = msg[0];
send_wait(0, top_object(), "call_attr", "api", "update_object_super", who, call_req_id.persistent_id, 0, "zattach", 1);
Also you can do the same without spel, create condition like this on form and call activity as OP=UPDATE, FACTORY=CR:
<PDM_IF "$cst.id" == "<UUID>">
docWrite("<input type='hidden' name='SET.zattach' value='1'>");
</PDM_IF>
Regards,
cdtj