If that doesn't work, it is not possible...As far as I know.
Only if you make 2 probes, one to graph and one to notify, on the one to graph just put "" in the error line and don't put anything in the graph on the 2nd probe....Is it possible to graph all the time and still have a notification on failure if a probe fails?
You can add devices by name but it has to be fully qualified...Nice to see Dude lumbering up.
Feature request: Add 'Name' to option when adding new device (not just IP).
In the error line any value returned is considered an error. You must return "" if you are not in an error state. In your case you are returning a value so it is in an error state.
You build a function to read the oid you are interested in then you use that function in a probe. Study the probe thread...How do you enter enter the OID for an specific item to monitor?