Highlighting an overdue date

[shaftdx]

ok I have a series of dates for our fleet of vehicles for service. I want to highlight the ones that are overdue. I know how to do it from todays date =today and all that but that is not what I need. The way I have it now there is a column that has "last Quarterly" which we physically type in the date. In the Next Column over is "Next Quarterly Due" which I take the previous date and add 90 days to that. What I am looking to do is Highlight the cell when those 90 days are done if we have not already done the check up to that vehicle.

 

[SFCSteve]

If all you want to do is highlight overdue dates I use the conditional formatting and it gives me flags, green, amber and red. Sorry if I am on the wrong track

This is what I’m currently trying to do but I cant seem to get my formats right, can you assist me?