I have some columns that ar filled by looking up a value in the entry array or lookup table. I would like to prevent entering new values (non existing) that are added to the lookup table (which happens now) or are added to the lookup array (which also happens now). In some cases I would also like to enforce a valid entry, rather than allowing blanks.
Is this possible through a function (or otherwise)?
And - is there a way to prevent entering doubles as a new entry in a table?