Thanks Acadian - what's the command? (You didn't say). Is it just "moveto player [ref ID]" ?
I bring up the ref id in the top center of the screen with the command console by either clicking on my mare (if she's near) or typing PRID 4BF2F (4BF2F is the Ref ID for 'My Black Horse'. Obviously it will be diff for My White Horse).
Now, with the horse's Ref ID up and displayed, any command you type in will refer to that REF ID. So, then I simply type in MoveTo Player, hit enter, close the console and voila: the horse appears by my character.
This is simply how I do it and I don't know if what you suggest works.
Let's say I'm approaching the gate to Bravil and want to bring my horse inside the town. I dismount, open the console and click on the horse (that brings up her Ref ID. Then I close the console and walk through the gate. On the other side, I open the console again and her Ref ID will still be displayed. Then I type in MoveTo Player, hit enter, close the console and there she is.
I hope that helps some.