Ok.. Does it matter if Spell is Open Very Easy Lock and the targeted lock is Average, does Open Very Easy Lock get experience then?
I usually don't train alteration that way, so I'm not 100% sure. But I think it does. You can try it. At lower alteration levels it should be easy to see whether the bar moves.
But using any alteration skill will help with the open lock spell. To self train, I usually buy or use a cheap protect spell and cast it alot on my character. That will increase alteration, and so allow you to buy higher level open lock spells even if you don't use Open that much.
Note that you cannot buy a Open Very Hard lock spell, but you can make one. Note also that Armor reduces spell effectiveness, so that may affect an open spells ability to work on some locks.
If you're going to be opening locks alot, you might consider increasing security skill and getting used to the lockpick minigame. I was terrible at it when I started but after a while, it gets easier. Also there is an item in the game that hugely helps with lockpicking, but I can't say what this is in the general forum.