DAX Measure: Filter in concatenatex

Hi,

I'd like to filter the concatenated column value in the DAX statement with CONCATENATEX, in this example:

Only Assignments with Relevant = Y should be shown for each account.

So in the end, the measure should only show Task A for Acc A, blank for B and Task D for C.

So far my measure works without the filter:

How can I now add the filter part in this measure?

Thank you.