Unshare a workbook

This question seems to have been asked quite alot, but never really answered.

I've got a problem where I've created a spreadsheet and protected it with a password so that only certain fields can be filled in and none of the formatting can be changed. I've then shared the workbook with changes but with no password.

this was working fine and everyone could access it with no problems.

I then need to edit some of the fields that have been protected so I set off to unshare the workbook. This is where i have run into problems.

I unprotected the share by unticking the box in share it gave me the options of yes and no which i ticked yes, it then saves the workbook but nothing happens it still says shared the top bar and I still can't unprotect the workbook to edit my document.

Has anyone come up with this before, im using excel 2002.

Cheers