I have a drop down list, with 16 names, and also 16 cells where the same drop
down list is displayed. What I want is this:

When e.g. the name "Ann" is selected in one of the cells (based on the drop
down list) I want "Ann" to disappear from all of the other drop down lists.
This to ensure that one name can only be selected once, and to make sure that
all names are selected at least once.

How do I do that?