Yes- you'll need to create a local administrator account on the workgroup server. Ideally, you can use the same username and password as what backupexec uses within your domain. And of course, both servers must be able to resolve the network name of each other- create hosts file if not.
You then can go through the Veritas remote Agent Installation and 'Add Remote Computer Manually' supplying the username, password and the local server name as the domain for the credentials.