Dim n As Integer = 1

while n < 17 'giusto per dirne uno
    Dim req As HttpWebRequest = CType(WebRequest.Create("http://fantagazzetta.com/download.aspx"), HttpWebRequest)
    req.Method = "POST"

    Dim postData As String = "key=voti&g=" & n
     
   '...ecc

    n += 1
End While