Normally, if there's more than one horse near a gate I send the unwanted horse to "Go Here," then unlock the gate and beckon the wanted horse through. When I'm feeling lazy, I go into Buy mode and with MoveObject enabled, simply put the horse where I want it.
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Sad day on Saracen Arabian Farm! I had all three of my human sims doing training. While I was observing Sabra and Abbie on the advanced courses, Clint was training on the International course. He caught fire and died before I could get him extinguished. In deference to his passing, all farm activities will be suspended for the balance of this (human day). Rest in peace, Clint. In Memorium, Clint's gravesite has been placed on the International Training Facility grounds. In lieu of flowers, please send donations to your favorite charity.