Disable form submit button whose workflow completed in MOSS

Object: After finishing workflow, Infopath template submit button should be disabled so that no one can change form.
Logic: set conditional formatting of submit button using workflow output field which denotes status from form library.
1. In Infopath->Tools -> data connection ->Add -> Create new connection -> receive data->next
2. Select sharepoint library or list -> next give url and … select list and workflow output field … -> finish
3. On submit button right click ->conditional formatting - >add field and value(completed status code) and set disable button .