Find duplicate values in a column, when both values have matching value in another

I have a situation where I have various "projects" with varying numbers of team members assigned to each. Each of those members may be assigned software "options", but cannot share options, nor can they be assigned more than one.
I need to be able to find and highlight any pair of duplicate values in my columns, but only if they both belong to the same "project" in another column.

Conditional Formatting rows is easy, as they only need to have more than one duplicate value.
Using =COUNTIF($D31:$G31,"<>")>1

Columns get tricky because I expect duplicate values in the whole column, just can't occur in the same group of rows, (Identified by project # in another column.)

Thanks, JeteMc. that works perfectly for truly "duplicate" values. Which I realize now is exactly what I asked, but what I was getting at is "TWO OR MORE NON-BLANK CELLS". My rows rule in my original post works fine, because it's only looking for any two or more non-blank cells in any row, thus the "<>", which is a single condition. The columns have to meet multiple conditions.