datanibbler - This works a treat. Need to do this in conjunction with DataNibblers Answer. (Note there may be a security issue linking to a hidden workbook sheet from another workbook)
Here is what you do in Excel 2003: (variations also work for 2007,10,13)
- In your sheet of interest, go to Format->Sheet->Hide and hide your sheet.
- Go to Tools->Protection->Protect Workbook, make sure Structure is selected, and enter your password of choice.
Once this is done, the sheet is hidden and cannot be unhidden without the password. Make sense?
(Given Excel's backward compatibility, I'm sure you can do this in 2007)