Good Morning, I asked this yesterday as well, I am now trying again but rephrasing. I have a Recorder field which is taken from the Employee Entity – Full name. The association used is Employee_MinutesRecorder I have a reference set selector where names can be selected which is taken from the Employee Entity – Full name. The association used is Employee_Minutes. In the reference set selector I want the name that is chosen as the Recorder to not be allowed to show in the reference set selector. I’m trying to do this as an XPath constraint but can’t work out what the expression should be. Am I on the right lines? if so can anyone let me know the expression please?