How do I Concatenate a url?

I am trying to concatenate a url for an ajax action. I will be a static url with the last portion being an earlier entered user text input variable. It has to be something like, "www.spl......"&"user.text" but i can't figure out the exact syntaxes to make it work, any help would be appreciated.

Set FullURL to "www.site.com/" & TextBox.text

or with the variable:

Set FullURL to "www.site.com/" & TextVariable