Editing text in comboBox & updating it in database column

Question

Hi

By using .NET functionality i have attached one column
with a comboBox. so when i click on comboBox it shows all the items in that column
now i want to add a row to the comboBox having text as "create new" by clicking which
user can add new entry to comboBox and ultimately to the database column.
so can anybody tell whether this is possible or not and if yes then please elaborate how.
thanks