[excel] Determine if a cell (value) is used in any formula

I am trying to reverse engineer an ancient program written using VBA in excel and formulas in cells. There are many cells with values scattered across everywhere. Is there a fast way to check if a cell (value) is being used in another cell's forumla; or if the cell is just sitting there doing nothing so that I can delete/igonore it safely? Thanks in advance.

I used the Ctrl+F find tool and it seems like it does work, but I just want to be sure if there is another better way.

On Excel 2010 try this:

1. select the cell you want to check if is used somewhere in a formula;
2. Formulas -> Trace Dependents (on Formula Auditing menu)