Highlight every other Project ID not every other row

I want to highlight every other ProjectID row in my detail section of my report.  
I know how to  highlight every other row in the detail section but would rather see it highlight every other project ID - which could have any number of rows.
In the below example: (I have suppress if duplicated on the ProjID) I would like to see all of ProjID 2 highlighted as a group and ProjID 1 and 3 would just be the crNoColor.  I tried moving all my fields to the ProjID group header but I got weird results.

ProjID  Date  Comment
1          1/7     blah blah
            1/6     blah blah
2          1/7     lkjl;kj;lkjlkj
            1/6     asdfasd
            1/5     asdfasdf
3          1/7     lkjlkjsadfk
            1/5      lkjlkjl;kjl;kj

Currently I am just using this to color every other row.
 
IF Remainder(RecordNumber,2)=0 THEN RGB(219,219,219) ELSE CrNoColor

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