Anyone out there a collection guru?

I wanna know how to replace an item in a collection.

i.e.

dim col as new collection

col.add "a"
col.add "b"
col.add "c"

'now replace b with z
'how do I do that.

What I have come up with is to remove B, then insert Z after a.

col.remove 2
col.add "z", ,a

isn't there a better way to do this?