I am looking for the following: I need a new entry type which has to
become a unique field of a given range. The user has to be able to
choose from available values.
The field is a "Priority" and there can only entry with a priority of a
priority between one and fifty in a folder at one time. So the field has
to be a list of any free priorities. Of course, if an entry is deleted
the priority is free again.

Any ideas?