Create a count measure

Hi Icey  or anyone,

Need your help on this one. I'm trying to create a measure that counts who got the passing score, but here's the thing, if the agent already got a passing score previously, that agent will no longer be counted even if they got a passing score on the succeeding tenure days.

Just like the below Output table, on row 1 Tenure 62, we have 3 agents as population, No Proficient/No of passers we only have 1 since only John got the passing score highlighted in green.  In row 2 Tenure 69, same population, now, on No Proficient, looking at the Table we have two passers, John and Mary, but since John already got a passing score on Tenure 69, John will no longer be counted, and the count should only be Mary since it's the first time she got a passing score. Same applies on row 3 Tenure 76.

Any help is greatly apprecieted.