The headline does not describe well what I am asking about.
I hava a table "Preparations" with substances. In another table "Preparationlist" I have selected some items from the table Preparations, that is the Preparationlist is a subset of Preparations, where IDf_Preparations (table Preparationlist) is related to ID_Preparations (table Preparations).
When I enter a new record in the Preparationlist, I have a drop down menu with all the Preparations listed. All this works fine. BUT I would like the drop-down list ONLY to contain preparations from the Preparations table that are not already in the Preparationslist (not selected before). This to prevent the same substance to be chose twice.
I imagine that it should be possible to achieve this with a smart relationship in the relationship graph, but I am not the one to figure out how to do it.
Jonas Möller Nielsen