Mailmerge in Word with ASP.NET

[RH]

Hi,
I'm trying to use mailmerge with Word2003 from an asp.net webpage
I'm using the following code:

Dim W As New Word.Application
Dim D As Word.Document = W.Documents.Open("maindoc.doc")
D.MailMerge.OpenDataSource("address.txt")
D.MailMerge.Destination =
Word.WdMailMergeDestination.wdSendToNewDocument
D.MailMerge.Execute()

For some reason I get an "Access denied" error.
How can I get it to work?

TIA

Remco