LordAndy,
It is possible to completely hide the contents of a cell using the "Hidden" option under Protection with the cell format set to ";;;". If you also "Lock" the cell the contents become not only invisible, but your users won't be able to access it and make any changes. I've found this invaluable when creating sheets for multiple users - keeps them from messing with the calculations.
If this is what you're doing SkipVought's solution will work, but you'll have a couple of extra steps to perform when recording your macro.
Hope this helps.