Drop down list

[sspatriots]

I've found great code examples on line of how to create a drop-down list that will allow a user to make a unique entry that is not already on the list as well as give that user to add that unique item to the list. I've also seen examples of how to make your drop-down list such that the user can select more than one item from a drop-down list. I'm posting this to see if anyone knows of a source that will do both down an entire column.

Any recommendations would be greatly appreciated. Thanks SS