There are significant differences between Outlook version  2000 and 2003.
If I were doing the coding, I would be sure and perform late binding to
let Excel & Outlook figure out how to allocate resources as appropriate.
Below is some code  I use to start an email  message from an Excel
spreadsheet. In it, I am only concerned with getting the addresses in
the bcc field, but you can see how I did it, and perhaps it will help
you.

#If EarlyBinding = 1 Then
Public objOLapp As Outlook.Application
Public objOLitem As Outlook.MailItem
#Else
Public objOLapp As Object
Public objOLitem As Object
#End If

Sub Test(strEmail As String)
On Error GoTo EH
Dim objOLapp As Object
Dim objOLitem As Object
Set objOLapp = CreateObject("Outlook.Application")
Set objOLitem = objOLapp.CreateItem(0)
With objOLitem
.Subject = ""
.CC = ""
.To = ""
.Body = ""
.bcc = strEmail
' .Attachments.Add '(path to the attachment,either hard coded or
variable)
.Display
End With
Set objOLapp = Nothing
Set objOLitem = Nothing
'Handle Errors Gracefully
Exit_EH:
Exit Sub

EH:
MsgBox Err.Number & ": " & Err.Description
Resume Exit_EH

End Sub

So you mean early binding should take care of the issue.

I would design with early binding on, and then release the code  with late
binding. That way while you are designing and testing the code with your
version of Excel and Outlook, you get as much help from intellisense as you
possibly can, then change the code so that it uses late binding when you release
it to others with different versions of Outlook.