Looking up the Latest Value for a Given Task Name

Hello, I use Power BI to compile information from multiple projects entered into Microsoft Project (MSP). The project name is associated with a Projects table, and date-level information is associated with a Tasks table. In a normal project, each design turn-in has a single date associated with it, but if the consultant messes up their submission, they are required to resubmit. It is valuable to us to show both turn-in dates for the record in the MSP schedule.

This is fine for individual projects, but it causes problems when producing reports pulling from multiple schedules. I am trying to write a formula that will lookup the latest date for a turn-in of a given name. In the below example, this project had two turn-ins for the 60% design level. I want my report to be able to pull the later of the two turn-in dates (simplified for illustrative purposes):

Using LOOKUPVALUE is fine for everything except the projects which have multiple turn-ins of the same plan set. I spent a long time combing through other threads to resolve this problem, and I feel like LASTNONBLANK is probably the way to go, but I can't quite get it to work. Any suggestions? Thank you!