Is there a way, using Javascript, to track what edits the form user made to a pre-populated text box? Idealy, just the changes would be copied to another text box.
If it is dynamic, run a script after pre-filling (or when opening the pre-filled form) which sets all default values to the field's values.
Then parse the fields and compare their value with the default value. When you have a difference, the user has changed something...
Hope this can help.
Max.