it should only effect forms that use the same design.
another option is to identify the class for the x-large form elements, and create a style section on the pages you want to override it on wit the new width.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.