What kind of a form are you using? If you are developing a custom module you can make your ASCX file inherit from PortalModuleBase, and that will immediately give you access to the UserInfo object which containers username, userid, firstname, lastname and a bunch of other user properties.

You will likely need to check with the vendor of that module for support for their products. But if they support DNN Tokens you can find a list of those tokens here. http://www.datasprings.com...