By Default all Cells are "Locked".
What you will need to do is Highlight each cell you want 'editable' and remove the check mark from the "Locked" field on the Protection Tab, of the "Format Cells" Window.
The key is after you do all that, you have to go and protect the sheet.
(In Excel 2003) it is Tools --> Protection --> Protect Sheet. Then you can pick and choose what users are allowed to do with the worksheet using the check boxes then put a password in and click 'ok'. Retype the password and you should be good.
