Redirect After Http 200

I have no idea if this is actually possible in plain asp but any help might
be welcome :

After a user has downloaded some content/file from my webserver (http_status
=200) I would like to redirect him to a file -lets say- "ThankYou.htm"

So basically sth like this

If Response.Status ="200 OK" then
Response.Redirect "ThankYou.htm"
Else
Response.Redirect "GetLost.htm"
End If

The question is : how would i implement this ONLY for the document to be downloaded ? The document to be downloaded is part of a collection from a DB query - so it is know to me as sFileName = rsPDF_ID("PDF_File")