Collection Classes

I'm implementing a library of COM objects using ATL.  I need to expose numerous collections to the client.  My primary clients will be written in VB, so the ideal resulting syntax would be:
v= obj(index).value
o= obj(index).otherValue
Or
v= obj.item(index).value
o= obj.item(index).otherValue

I've seen these two variations in syntax used before, how do I implement them with ATL?  Please provide references and code examples.

Thanks.