Set analysis ? class function or conditional flag ? Which would be best ?

[claudialet]

 Hi all

Which method would be best here ?  class ()  ? Flag ?  

Here is my expression : 

round(Avg({1<Category={'Conditions'},Dept_ID={'1'},Task_ID=P(Task_ID)>} Actual_Score)/10000,0.001)

The requirement is to show all associated dim name that are less that < .50  or 50%

This front end expression does not work in load script