Is there a way to populate a custom field for every node in a group?

I am new to Solarwinds and taking over a partially configured environment.  The guy that set up all the alerts used a custom-properties field called ServiceLevel as a trigger to send alerts.  That being said he never populated the field at the node level.  Is there a way that i can push that out at the group level so the nodes inherent it? Or possibly a way to do it through SQL?