Hi
Mike Glen in his tutorial on Project uses the stoplight concept in relation
to costs...
http://pubs.logicalexpressions.com/Pub0009/LPMArticle.asp?ID=403
and here's a formula i developed in response to another post on a similar
question
IIf([% Complete]<>"100",IIf([Finish]-[Baseline Finish]>7,"over
week",IIf([Finish]-[Baseline Finish]<=0,"on target","week")),"NA")
which compares (and returns text) based on the difference between finish &
baseline finish. You can use the text outputted by this formula (modified
to what you want) to link to the graphical indicators.
see how you go with this and if you require further assistance, please feel
free to post back.
Cheers
JulieD