Sub XMLPost()
Dim xmlhttp,sData As String

    With ActiveSheet
        sData = "x=" & URLencode(.Range("A2").Value) & _
                "&y=" & URLencode(.Range("B2").Value)
    End With

    Set xmlhttp = CreateObject("microsoft.xmlhttp")

    With xmlhttp
        .Open "POST"," http://testingHttpPost/",False
        .setrequestheader "Content-Type","application/x-www-form-urlencoded"
        .send sData
        Debug.Print .responsetext
    End With
End Sub

对于URLencode功能,请参见此处：How can I URL encode a string in Excel VBA?