You'll have to provide a StringBuilder, then send the result of that to Response.Write.
Dim myResponse As New StringBuilder()
Using sw As New StringWriter(myResponse)
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
sw.Write("...")
Response.Write(myResponse.ToString())
End Using