[vtx1800]

In the custom BB code area, you can set the BBcode var, and the html to use for that var. you use {param} as the var in the html. Example:

[test]Testvar[/test]

In the ACP, your html would be <a href='http://www.domain.com/user/{param}'>My Profile</a>

Then when the code is used, it will return <a href='http://www.domain.com/user/Testvar'>My Profile</a>