Validation List to Grow with Entries?

Hi, Not sure how to work the title, but I'm wondering if you can somehow create a list that lets you enter new items or pick from the existing items -

For example, Column I will have the name of an insurance company for each client

There are 2000 rows of clients

I want to enter any new insurance companies in Col. I or pick from the existing ones in Col. I to eliminate typos

(there might be blanks between what was entered and new items, so the auto-type may not work)

Not sure if this is worksheet or VBA function

Thanks!