Trim or Edit Activities

i often forget to stop my watch immediately upon completing and activity. Sometimes I have to stop for a train crossing, or to wait my turn at a trail obstacle.I would like a tool to easily declare on the map in Garmin Connect where or when the activity ended, or make a few minutes to be deleted, and have it remove any of those data and recalculate all of the statistics.

I have several friends who have this issue, and I'll be very surprised if this isn't a common lament. I check these out - http://www.dcrainmaker.com/tools - but they seem kinda complex for my limited skills and patience.

Thanks!

Andrew