Specific drop-down of an entity

My entity has 4 attributes: Storage location (string), status (enumeration), X (enumeration) and Y (enumeration).   X and Y are to be seen as coordinates and, when put together, result in the storage location. Each storage location is also assigned a status (free, occupied, blocked).  In an input mask, only the storage locations that have the status free are to be suggested via a drop-down.   How do I achieve this?
1 answers

you can specify a constraint on the selectable objects tab of a reference selector when selecting storage locations