I do this (not for poker, but for other purposes) with a program called ShortKeys, www.shortkeys.com (http://www.shortkeys.com). They have a "Lite" version that's free.
You can input keyboard shortcuts and what you want them to expand to, and whenever you type the shortcut you'll get the full character string. I use it, for example, to display my full name by typing only my initals.
Just make sure you have it turned off when you don't want to use it, or you'll be typing things you don't want all the time!