Changing a cell colour after a set time

[Spyke]

This ones been bugging me for a bit now...

I have an overview sheet that reads from the other tabs using an IF formula.

E.g.

If i change a few cells on Sheet 2 then on the overview sheet it will put A in the relevant cell. If a different criteria is met it will put B in the cell. etc etc. The formula reads:

=IF(AND(Mouchel!C25="Yes",Mouchel!D25="No"),"A",IF(AND(Mouchel!C25="No",Mouchel!D25="Yes - Returned"),"B",IF(AND(Mouchel!C25="Yes",Mouchel!D25="Yes - Agreed",Mouchel!E25="No"),"C","")))

Is there something i can include in this formula so that when it changes to A, B or C becuase the criteria is met it starts a timer and changes colour after 2 weeks if it does not change. E.g. If the cell turns to reading A and it remains like that for 2weeks the cell colour will change red, however if after 1 week it is then changed to B the timer will restart?

Its quite hard to explain and porbably not do-able but thought id give this place a go

Thanks.

[Spyke]

Or any ideas on how to get a similar outcome?