Formula to highlight at risk items in Gantt Spreadsheet

I'm using the Gantt spreadsheet template in excel to manage a number of projects and tasks in one place.  I've been trying (and failing) to figure out a formula that would highlight at risk items.  Here's what I'm trying to do, but the actual formula defies me.

 

Column B is the task name

Column D is the plan start date

Column E is the planned duration

Cell I2 is the current week

 

If I2-((D+E)-1) = 0, highlight B red

If I2-((D+E)-1) = -1, highlight B yellow

 

How can I make that happen?

Thanks