I don't think you can use a variable in regex.
One thing I did notice, however, is that if you're trying to replace more than just one instance of something, you can split on something, then join on "".
This will replace all instances of variable something with "". If you have two or more spaces in the resulting string, then use regex to replace all double-or-more instances of space with just single space.
If anyone knows of a website that can offer ColdFusion help that isn't controlled by neurotic, pedantic jerks* (stackoverflow.com), please PM me with a link.
* The neurotic, pedantic jerks are not the owners; just the people who are in control of the "popularity contest".