help with custom sort

[Ron Noice]

I have a field containing several items including one for month/year pairs such as:
Oct 2005
Apr 2005
Feb 2004
Jan 2006
Apr 2005
Aug 2005

Is there any clever way to get these lines sorted chronologically? What I've been doing so far is generating a real date from them:
Oct 1, 2005
Apr 1, 2005
etc.
in a hidden item and sorting that. 
This works but I'm betting there's a way to do a custom sort thingee that works directly from the original values. But so far I've come up with nada. Any clever ideas?

... Ron