Dude are you trying to replace the object at ith position?
If yes, then you should better take that object@ith index into some object and work upon it.
binding list lets you upate/add/delete the object but you can't replace the object reference altogther
For doing this remove the requirec object and add a new one.
This is exactly the error says "The list must be an IBindingList to AddNew"
hope this helps :)