Stereo code error

Richiebuoy

After a battery disconection on our tow car I had to put in the code for the stereo, unfortunatly I kept putting (3 times) the code for our other vehicle and now just get "ERROR" come up when I turn the stereo on ( in other words it wont let me put in the
code, which I now have the correct one). Any solutions to this or is it off to the dealer ?