自前のエクステンションを使います。
サンプル
GraphicsWindow.BackgroundColor = "skyblue"
button = Controls.AddButton("run", 200, 100)
Controls.ButtonClicked = onclick
Sub onclick
WC = Text.GetCharacter(34)
CR = Text.GetCharacter(13) + Text.GetCharacter(10)
code = ""
code = code + "Function setup(a)" + CR
code = code + "url = " + WC + "http://ohisamallc.dip.jp/test21.php" + WC + CR
code = code + "key = " + WC + "txt=test desu2" + WC + CR
code = code + "Set obj = CreateObject(" + WC + "MSXML2.ServerXMLHTTP" + WC + ")" + CR
code = code + "obj.open " + WC + "POST" + WC + ", url, False" + CR
code = code + "obj.setRequestHeader " + WC + "Content-Type" + WC + ", " + WC + " application/x-www-form-urlencoded" + WC + CR
code = code + "obj.setRequestHeader " + WC + "Content-Length" + WC + ", " + WC + "length" + WC+ CR
code = code + "obj.send key" + CR
code = code + "setup = obj.responseText" + CR
code = code + "msgbox setup" + CR
code = code + "End Function" + CR
a = Class1.VBSrun(code)
EndSub