adding collections.
i have added a collection to my project in a class module
but i get errors when trying to run it
what am i doing wrong help me please???

Code:
Private colDetails As New collection
'then using a function
 colDetails.add newDetail, CStr(.id)
'and i get a runtime error '457'
'the key is already associated with an element of this 
'collection any ideas what that means????