请教大神

我抄下面的代码做了一个程序，数据被提交了，但现在的问题是网站显示收到了两次数据，这是怎么回事?怎么改进？
Function XMLHttpPOST(ByVal url As String, ByVal PostData As String) As String
Set XML = CreateObject("Microsoft.XMLHTTP")
With XML
.Open "POST", url, False
.setRequestHeader "Accept", "*/*"
.setRequestHeader "Accept-Language", "zh-cn"
.setRequestHeader "User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)"
.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
.setRequestHeader "Referer", ""
.setRequestHeader "Content-Length", Len(PostData)
.setRequestHeader "Connection", "Keep-Alive"
.setRequestHeader "Cache-Control", "no-cache"
.Send (PostData)
Do Until .ReadyState = 4
DoEvents
Loop
XMLHttpPOST = .responseText
End With
Set XML = Nothing
End Function