you can build a javascript validation that includes those characters, or you can use a frontpage webbot to build it for you. Im not generally a front-page fan, but the form validation script it builds is impressive and fast. build the form in front page, run it on a frontpage enabled server, then copy the validation script from the source-code. there is an option under validation that allows you to list specific characters. I dont think that option is availabel in Dreamweaver yet.
Jon