you need realspeed or gpsresults, then you can select a time range and save the selection as a new file. If you don't have it maybe someone in your team would....
He means you need to open the file in a stand alone analysis program like GPS-Results, RealSpeed or GPSAR-Pro. You can then easy trim the drive home out of it.
There are other ways to do it, but those are the easiest I think.
Alternatively, if any of your Team or mates have one of those programs they might do it for you.