Hi Melina,

I'm sorry to hear that you're having trouble with conditional formatting in Excel 2007. It sounds like the formatting isn't updating automatically when you delete the contents of a cell, but it does update when you switch to another program and then back to Excel.

One thing you can try is to check the settings for automatic calculation in Excel. Here's how:

1. Click on the "Office" button in the top left corner of the Excel window.
2. Click on "Excel Options" at the bottom of the menu.
3. Click on "Formulas" in the left-hand menu.
4. Under "Calculation options," make sure that "Automatic" is selected.

If "Automatic" is already selected, you can try turning it off and then back on again to see if that fixes the issue.

Another thing you can try is to force Excel to recalculate the sheet by pressing the F9 key. This should update the conditional formatting immediately, without having to switch to another program and back.

If neither of these solutions work, there may be an issue with your installation of Excel. You could try repairing or reinstalling Excel to see if that resolves the problem.

Let me know if you have any other questions or if there's anything else I can do to assist you.