If you are operating the program in Playlist File Mode the following Preset Filter Codes enable flagging of jockey and/or trainer changes in your UDMs:
BarnSwitch: BSWITCH=1 require barn switch today BSWITCH=0 avoid barn switch today BSWITCH=N avoid barn switch in record BSWITCH=Y require barn switch in record
JockSwitch: JSWITCH=1 require jock switch today JSWITCH=0 avoid jock switch today JSWITCH=N avoid jock switch in record JSWITCH=Y require jock switch in record
Q. What's a barn switch?
A. In JCapper a barn switch is tied to a change in trainer name(s). A horse is said to be making a barn switch today if the trainer listed for today's start is different than the trainer listed for the horse's previous start.
Q. What's a jock switch?
A. In JCapper a jock switch is tied to a change in rider name(s). A horse is said to be making a jock switch today if the rider listed for today's start is different than the rider listed for the horse's previous start.
These new preset filters can provide some interesting results when combined with other factors - including the XthStart for both rider and trainer filters.
Hint: Some trainers are actually pretty good when a horse they've had in the past (and lost to someone else) ends up back in their barn again.
If you are operating the program inSQL Mode (unfortunately) the closest you can get is XthStartRider and/or XthStartTrainer - which as you mentioned - is not the same thing as a rider or trainer switch.