Zend certified PHP/Magento developer

Conditional Formatting based on last date being greater than todays date

I am trying to highlight a blank cell with Red if the date in the preceeding cell is 2 days later than today’s date.

For example

Cell G5 has the date something happened

Cell H5 is the next step in the process

If cell H5 is blank for 2 days past the date in G5 I want to highlight red but then once the date is entered into H5 I want the highlight to go away… or turn green