how to change the filterExpression on custom selector?

Hello. i finally managed to get a User selector working using this as an example: http://www.sitefinity.com/blogs/radoslavgeorgiev/posts/12-02-27/creating_one_to_many_relationships_in_dynamic_modules.aspx 

I am getting the users using the service: "~/Sitefinity/Services/Security/Users.svc/"

the problem is that the service doesnt return a Title variable, it returns a DisplayName, so i need to override the filterExpression to use DisaplayName instead of Title, Author, PublishDate.

how can i do this in the example above?  i have looked for other articles and they mention to override the CreateChildControls but they dont mention where that might need to be done.  I dont have CreateChildControls or know where it is getting called in the example above.

any help is appreciated.  thanks.

OK i found where to override CreateChildControls but ContentFilterBuilder doesn't seem to exist anymore or is simply not apart of TextField.  so what's the solution now?