How to set background color for expression values at dimension level?

[#1]

The following expression sets the background to bright green for an expression cell for the lowest values of the dimension Phone for each TestName. 

if (  

               (

                              (

                              // Puts bright GREEN background on lowest value in TestName

                                   (SUM(tblResultsRaw.Result)) = Aggr(NODISTINCT Min(tblResultsRaw.Result),tblResultsRaw.TestName)

                              )

               )

               ,rgb(0,255,0)                

)

However, if I have another dimension to which TestName rolls up to in a pivot table such as Category, how to I also get the Background color to be set for the lowest value for each Category and Phone.

See the attached, you can see where the highlighting is fine when the TestName dimension is showing but when collapsed, no background is set.

Anyone have an idea what I am missing?

Thanks,

D