Invoice entry -changing default value in invoice register field depending on respnsibility

Hi, I am hoping someone can help again. We have recently set up a new operating unit in Northern Ireland Water to allow entry of invoices under the separate operating unit. We have set up a separate responsibility for invoice entry. One is called HQ Invoice Entry and the other is called Alpha HQ Invoice Entry. On the invoice register field we have set up a number of default values but we have been asked if we can change the default of the value under field Division so E will appear as default under responsibility HQ Invoice Entry and A will appear as default under responsibility Alpha HQ Invoice entry.  Please see screenshots below. I can change the default value for the field Division from the descriptive segment but have been unable to find a way to change the default value so that a different value will appear depending on the responsibility chosen. I have also  tried changing  the default type for the field Division to sql statement and have tried to write a statement to bring in the seprarate values but I  keep getting an