Flex :: Get Users From An ArrayList & Another Field For Creating A New User?

I'd like to create a combobox which will get users from an arrayList & another field for creating a new user. for example when i open the combobox i'd like to see the rows :

Create new user
User A
User B

where the users come form an arrayList and the "create new user" option is always there.

How can I do it?P.S I don't wan't to add "create new user" obj to the arryList - so this is not a desired solution.