Strict Data Typing a Combobox...error

Hey all,

I have a combobox named:
[COLOR=Blue]moduleDropDown[/COLOR]

Here is what I did in actionscript:
[COLOR=Blue]var moduleDropDown:ComboBox;

[COLOR=Black]This is the error I get when I test my movie:[/COLOR][/COLOR]
[COLOR=Blue]Error Scene=Scene 1, layer=Actions, frame=1:Line 11: The class or interface ‘ComboBox’ could not be loaded.
var moduleDropDown:ComboBox;

Total ActionScript Errors: 1 Reported Errors: 1

[COLOR=Black]Can anyone tell me what I did wrong?

Thanks.[/COLOR]
[/COLOR]

You have to import the class first (or use the fully qualified name):

import mx.controls.ComboBox;