Alert dose not Work whan Including Sum in the Formula

Hello all,

I am working on below table in Webi.

And I need to show the Green/ Red alert Images based on the "%" value in the last column comparing to the "total %"

as follow:

Red: "=[Sales_%] < Sum([Sales_%])"

Green : "=[Sales_% > Sum([Sales_%])]"

I am using the Conditional Format. When I try the above formulas comparing to a number as below, It works fine. However, when I replace the numbers with "Sum([Sales_%])", the images are not showed.

Red: "=[Sales_%] < 100"

Green: "=[Sales_%] > 100"

Anybody can tell me what is the problem ? and how I can apply this conditional formatting using "Sum()"?

Thanks,