Can I generate a username based on first and last name?

Since I'm using the vBulletin plugin, and since vBulletin uses the username from aMember as its username, I'd like the aMember username to be the first and last name (with a space in between).

Is it possible to have aMember generate this username for new users using their First and Last name from the signup form?

I'm using aMember 3.1.8PRO.