You can mark a cell as "hidden" on the Protection tab. That actually means that it will not show any formulae or text values in the formula bar.

So, if you lock the cells, hide the cells, protect the worksheet (primarily prevent people from accessing locked cells) and then set the visible state to xlSheetVeryHidden in the VBA properties for the sheet, it will stop the majority of people.

I'd be inclined to suggest that this sheet has links to a master sheet and only picks up information that is essential to the workbook.

And, of course, the VBA project must be locked for viewing with a password.

All that said, abousetta is absolutely right (and got the point in first) that Excel is inherently insecure, not in a poor self esteem sort of way, and protection can be broken relatively easily.

Regards, TMS