Hello Mark -
You may want to try monitoring the Property Path "Locals.ResultList[0].TS.SequenceCall.Status" from within your process model after the MainSequence Callback, you'll definitely be able to sniff for Passed/Failed status, Error is a bit trickier since if you don't 'ignore' the error, the report's status will be 'Error' and if you do ignore the error, your status will be Terminated, but the only place the Error will be tracked will be in the per-step information.
To aid in monitoring what happens when a Terminate occurs, I recommend you enable the 'break while Terminating' and 'Trace while Terminating' options in TestStand.
--Regards,
Elaine R.
National Instruments
http://www.ni.com/support