Hey Cliff, You'll need to use that in a blank column on a task or issue report. It should look like this: I used the exact same code as was pasted above. One thing you can consider once you get it working, is to add the word Days so it looks like this instead: Here's the expression I used:
valueexpression=CONCAT(WEEKDAYDIFF({actualStartDate},{actualCompletionDate})," days")
Hope this helps! Thanks, Dustin Martin Tier 2 Assigned Support Engineer Workfront