Hi.
I have a grid in which in one of the columns I need a combo or list box that works as follows:
1.- Lists all values previously entered in the field;
2.- Shows no duplicate values
3.- When an item in the combo/list is selected, its added in the new record, or changed in a previous record;
4.- Allows the user to enter a new value if no similar value had been entered before.This new value should be added to the record and shown in the list immediately if a new record is needed.

I tried a Select-Distinct-SQL statement in a combo box, but this won't allow me to add a new value.
What properties should I set to achieve this result?
TIA
Ulises.