Alternative for LOOKUPVALUE in M

[mickeydjw]

Scenario:  I have a dataset with Work Item ID and Parent Work Item ID.  I'm trying to create a hierarchy within the 2 to build some reports.  When I try to set it up, I receive the error that the Parent Work Item ID doesn't have itself listed in the Work Item ID, to the tune of about 120k items.  I can create a column, Lookupvalue that will give me the work item info, but that doesn't allow me to remove them from the query, so I won't be able to build my Path.

How can I remove the cases that don't exist from the query using M?

References:

New Parent ID = LOOKUPVALUE('Work Items - Today'[Work Item Id],'Work Items - Today'[Work Item Id],'Work Items - Today'[Parent Work Item Id])