Upgrading VBA 6->7 causes error: If Exists in Collection - vba

Question

VBA6 code (Excel) worked great. Upgrade to Office 2010/VBA7, code breaks.
Using code from SO:
Determining whether an object is a member of a collection in VBA
Public Function Contains(col As Collection, key As Variant) As Boolean
Dim obj As Variant
On Error GoTo err
Contains = True
obj = col(key)
Exit Function
err:
Contains = False
End Function
I get run-time error 5: Invalid procedure call or argument.
It doesn't make sense to me though because the error occurs on the obj = col(key) line which should be covered by the On Error GoTo err statement, but it stops.
Other If X exists in collection type solutions have the same problem.
Instead of fixing the broken code, what I really need is to be able to see if a record is already set for a collection, if that can be done some other (new) way in VBA7, that would solve the problem as well (I can dream).

Answer 1

I find that if I change specify an object, e.g., a worsheet, it works:
Public Function Contains(col As Collection, key As Variant) As Boolean
Dim ws As Excel.Worksheet
On Error GoTo err
Contains = True
Set ws = col(key)
Exit Function
err:
Contains = False
End Function
I call it like this:
Sub test()
Dim ws As Excel.Worksheet
Dim coll As Collection
Set coll = New Collection
For Each ws In ThisWorkbook.Worksheets
coll.Add ws, ws.Name
Next ws
Debug.Print Contains(coll, ActiveSheet.Name)
Debug.Print Contains(coll, "not a worksheet name")
End Sub
I get True for the first call and False for the second.