如何用API打开QQ的群聊天窗口？

Private Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long
Sub ttt()
ShellExecute 0, "open", "tencent://message/?uin=" & "QQ个人号码" & "&Site=LG&Menu=yes", "", "", 1 '打开QQ会话窗口
End Sub
上面的个人号码可以打开，为什么换成群号码就打不开，都已经是群成员了怎么还打不开，还提示加为好友？