Set grades using webservices and core api.

Hi ,

I working on external application from which i want to post grades in to gradebook without change php code in moodle. I post grades using web services or Core API only change in to php code in external application . Is it possible.

Example:- I add External tools in moodle (Using external tools plugins),that page are redirect to another page and that page, I have given any test show i want that this grade automatic show in to gradebook without change in moodle php code,only change in external page.

Any one know about that so Please help me.