Hey, I figured it out to anyone who is interested.
Code:
ServerAdmin noc@xainet.com
ServerName www.ebarg.com
ServerAlias ebarg.com "^(a-zA-Z0-9_.)+$".ebarg.com *.ebarg.com
DocumentRoot /my/path/to/root/
The last ServerAlias directive is redundant, but I left it in there anyway.
Maybe someone can find this handy.