mysql数据库的存储过程这段代码如何保存，被vb调用

begin

Set Comm = CreateObject("ADODB.Command")

 With Comm

 .ActiveConnection = Conn

 .CommandText = "CALL tt(@a)"

 .CommandType =&H1 'adCmdText .Execute

 .CommandText = "Select @a 'ReturnVal'"

Set objRs = .Execute

MsgBox objRs("ReturnVal")

End With

objRs.Close

Set objRs = Nothing

Set Comm = Nothing

end

出现1193错误