help with CollectionEditor(string) and GetStandardValuesSupported

[Brannon]

I have a TypeConverter that displays an exclusive list of possible
strings for a certain string property. That works great. In a different
class, I have a list of strings with the same limitation. I want a
CollectionEditor that will limit the string values to those of my
converter and limit the list so that its entries are unique and forced
to be one of my approved string values. Can somebody give me some
pointers on this?

It appears that I would override CreateInstace, scan through my
existing list and select a new value not already there for the default.
Can I return null on that if I don't want the user to return any more?
How do I limit the selection in my type converter to not include other
items already in the collection? How do I even set a type converter for
use int eh CollectionEditor?

Thanks for your time,
Brannon