Code to prevent CT completion with checked out files

Hello PDM-Link gurus,

What would be the code I need to put into the Complete Transition of a Change Task user activity to prevent them from completing the task if any of the Resulting Object files on that change task are checked out, and spit out a popup window saying "Please check in all Resulting Objects before proceeding"? If a Set State robot hits a checked-out file it freezes the task with the oh-so-fun Failed Queue Entry error and we've been getting hit by that a couple of times now, so I need to prevent it.

Please advise,

Daryl