How to: update field in database via text box on mod options area of User Profile

[b.h.]

Trying to make a plug to modify a FID field in the mybb_userfields table.

I want a text box with a submit button that will update the field with the data in the text box.

This will be located in the Moderator Options box on the users profile page

Can some one direct me with the code: for the update_querry