There are several different methods of highlighting cells with formulas.
If you are using Excel 2007, follow these steps instead:
Press Ctrl+F3. Excel displays the Name Manager dialog box.
Click New. Excel displays the New Name dialog box.
In the Name field (at the top of the dialog box), enter a name such as FormulaInCell.
In the Refers To field (at the bottom of the dialog box), enter the following:
Click OK. The New Name dialog box disappears, the Name Manager dialog box reappears, and the name you defined is listed in the dialog box.
Now you can follow the techniques previously outlined for setting up the conditional formatting. The only difference is that the conditional format should check for the following formula, instead:
This works in Excel 2010 as well (file must be saved as .xlsm) and I think it should work on Mac as it has same conditional formatting capabilities and macro support.