Ability to suggest a new term

Hi everyone,

I'm using content taxonomy module in one of my content types in a dropdown list where the user select a term, the node created will display an image corresponding to the term via taxonomy image module.

I want when the user select a specific value of the dropdown list "others", that he can add by himself a term he didn't find in the list using a textfield for example, but the term need to be approved by the administrator.

After approval the node can be updated.

I want to know how to do that, I don't know if there is a CCK field which can manage that ,

Thanks for help,