Creating Named Method for user defined method

I have written a method on the Service Request BC to set address fields based on a value selected from a pick list.  The method is called from a BC user property On Field Update Invoke X, "Service Street Name",  "Service Request", "SetStreetFields"  The method is defined in the BusComp_PreInvokeMethod.  The method works fine when the street Name is updated.  The problem is when another method performs an address postal validation and it attempts to update the Street Name.   When that happens it throws an error message "The specialized method 'SetStreetFields' is not supported on Business Component 'Service Request' used