//Get the document that emitted the CheckIn event
wt.doc.WTDocument targetObject = ( wt.doc.WTDocument ) ((wt.events.KeyedEvent) event).getEventTarget();
//Check if the targetObject represents the primaryBusinessObject, if so the PBO has been checkedIn , hence set result to "Checked In"
if ( targetObject.getNumber( ). equals(((wt.doc.WTDocument ) primaryBusinessObject). getNumber( ))){
result = "Checked In";
}