Trying to measure elapsed time with a record that appears on more than one row of a table

[NCato]

I've got data from our SQL server, coming from a Dynamics AX installation. We have warehouse picking journals that often consist of multiple lines.  The way my table is presented, is that some information from the record header is joined on as a reference on the line data. Here's an example of a two line picking journal.

I'm working with some creation and modified times, and I've created a simple measure to give an elapsed time, to show how long it was until the work was completed:
 

Elapsed Picking TIme =

SUMX(PickingData, PickingData[MODIFIEDDATETIME] - PickingData[CREATEDDATETIME])

I want to buld a visual that shows the elapsed time, per record header. So something like this, but you can see that when I take out the line info, it builds a sum of the time result for both lines.



How best could I acheive this? Change my measure, or change my approach on the visual?

[Greg_Deckler · Accepted solution]

Perhaps try changing SUMX to AVERAGEX

[NCato]

Thanks, I imagine that is a perfectly good solution, but in my case I'm working with test data at the moment, which isn't finalized, and will probably get my developer to build me a calculated column, rather than worry about this in the BI report.