Need help with project status formula

[benwahchang]

I've attached a spreadsheet with the data I will be working with. I'm looking for help with writing a formula that will indicate whether a project is on time < 3 days overdue returns a 1 (green), > 3 days, but < 6 days overdue returns a 2 (yellow) and anything over 6 days would return a 3 (red). I'm looking to have the actual duration compared to the planned. The problem I am having is that the entire planned duration will be populated at the start of the project and the actual will get filled in as it goes. I am having troubles thinking of a way to write the formula since I can't really do it based on comparing the SUMS of each column (F and G). I also want it to correct itself in that if one task takes 5 days longer than it should have and then another task takes 5 days less than it should have then it should say the project is back on time. The file was crashing a while back when someone else tried opening it. Please let me know if that is the case here. Any help is greatly appreciated.

[benwahchang]

Does anybody have any other suggestions as to how to track the overall project status based on the data in the above post?