Lookup or Rollup Project Online data from a Detail to Summary

[Mercaptan]

Hi - A bit new, but have a particular issue.  I'm trying to get a formula for a Custom Column in Power BI to either 'Lookup' or 'rollup' some data from a particular Detail task field to a Summary task field so I can then hide the Detail task from the table.  I have a column called "Type" that uses a lookup table that users flag the Summary as "Description" and then the particular Detail task that I want data from as "Submission".  It is indented beneath the Summary as you can see from the TaskOutlineNumber Row.  I can see that the 'TaskID" of the 'Description" Type task is the same as the "ParentID" of the Detail task with 'Submission' Type - so I thought I could find the detail task for a Summary that I want to get the data from using that.  So I want to find the data in the "ChildSubDate" column of the 'Submission' task to then populate the 'Description' tasks "Submission Date" field.  That way I can have the Submission date (driven from the Submission task info) to show on the same line as the Summary (Description task) and then not need to show the 'Submission task.  Does that make sense?  Any cool ideas?  Thanks!  Here is the simple table I described:

[v-yuta-msft]

Hi Mercaptan ,

What's your expected result? Could you clarify more explictly about your logic and expected result?

Regards,

Jimmy Tao