user story and task rollups

Not sure if this is the right forum, but here is the issue:  I am tryin to create a sioimple report which shows all client costs (charges) to date.  I am using one view table from TFS_Warehouse (on-prem TFS) and anotehr table which has the resource info (name, rate, etc.).  I have created a measure which calculates the cost based on the rate and completed work at task level.  Now I need to show the rollups to the uer story level where the client is tagged.  Is there a way to use DAX, or another means, to associate the user stories with the child tasks so I can make that calculation?  Any help would be appreciated.