I collect two pieces of information related to wait time.
My excel formula is" Wait time = Start time - Arrival time". Here is the format for the times, minus the quote symbols. "2/22/2013 1:34:47 PM".
I have tried date part using "DATEPART('minute',[CUSTOMERARRIVALTIMELOCALTS] )+(DATEPART('second',[CUSTOMERARRIVALTIMELOCALTS])/60)" but I keep getting negative numbers, I believe this is because I might have low minutes on the Start time, such as 5 min after the hour, and high min on the arrival time.
If they are both real datetimes, then you should be able to do datediff('minutes',[ticket time],[arrival time]) assuming that the ticket time is the later event.