Thank you for assisting and looking!!!

OK, so we have a 4-month process that consists of 15 milestones, each having a specific amount of time allowed to complete. The time allowed to complete for each milestone varies per milestone (some take 3-days, some are 7 days, 5-day, 14 days, 10 days, etc).

I need a formula to show that if a milestone is completed on time, a corresponding cell turns green. If it is 1 - 4 days late it is yellow. If it is 5 or greater days late it turns red.

For example: if milestone A should take 3 days to complete and it starts on 01Sep13 and it is completed by 03Sep13 then the corresponding cell will be green.
Milestone B should take 7 days, and in a perfect world it should be completed by 10Sep13, but it is delayed and completed on 12Sep13, so the corresponding cell will be yellow.

Now here is the tricky part, Milestone C (which should take 5 days) in a perfect world should be completed by 15Sep13, but since Milestone B was delayed it is starting 2 days late. If Milestone C is completed in 5 days (started 12Sep13 and end 17Sep13), how do I show that milestone as Green, but the overall project in yellow because it is 2 days behind schedule?

We have a tracker spreadsheet where we have to put all the dates in. I need a formula that shows the current status in color for each of the 15 milestone based on the dates I enter and the allowed time for each milestone in one column AND another column that shows overall status of project in color

The intent is to track which milestones allowable time to complete (after multiple iterations of this process) are just unattainable or where allowed time can be shortened.

I hope someone can help or am I asking something that is too difficult to create and would be better off hand jamming everything in there myself?
Thanks,
Travis