|Why do you say that the threads suggested by Mike don't meet your requirements?|
From everything you've told us, Conditional Formatting with the following 2 rules sounds like the way to go.
I just tried this in Excel 2003 and it works fine for me. I don't have 2007 on this machine, but there's no reason that the same rules shouldn't work for in 2007.
With "today" being 6/29/2011...
6/21/2011 turned H3 Orange
6/22/2011 turned H3 Red
Isn't that what you want?
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