conditionnal format matrix

Hi,

I've got a matrix that display a measure that is the first day in the month where i've data in my dataset

i'd like to format the cells when the value is empty or greater than 4 in red.

for that i try to select the measure in the conditionnal formatting but PBI doesn't allow it.

When i click on the measure, the field remains empty

it is possible to select a measure ?

do i have to set the styles in rules or field values ?

Thanks !