Protect Sheet but Hide/Unhide Columns

I have a speadsheet that has 27 columns for time entries, however employees seldom need to use more than the first 12 columns. I need to protect the sheet but would like the employees to be able to Unhide the columns when they need to use them, then reHide them. I can't find this as an option in either 2003 or 2007. Any suggestions?

Thank you for your help,
Ray

When you protect the sheet there are several options. put a check in the box for format columns and even protected you can unhide columns.