Dennis @ PerfectForms
I will assume that by universally unique you mean that it is not repeated in this closed system. In its present state it is not, but that would not be hard to accomplish.
After creating the GUID submit the form so it creates an instance. Create a connection to the form. In the form as part of the behavior send the resulting GUID as a send parameter. If there is a match then wipe it clean and start over.