what are the values for second parameter value for CreateParameter in ASP

Hi
i want to call sql server storedproc (myproc) from asp code (classic ASP)
create  PROCEDURE [dbo].[myproc]
(
    @mailid            uniqueidentifier OUTPUT,
    @user_guid         uniqueidentifier,
    @mailtype          integer,
    @toaddress         varchar(128) = NULL,
    @subject           varchar(256) = NULL,
    @Textbody              varchar(MAX) = NULL,
             @std_msgid         int = NULL,
    @att1              varchar(128) = NULL,
    @att2              varchar(128) = NULL,
    @att3              varchar(128) = NULL,
             @HTMLBody           varchar(MAX) = null

)
...
how to pass parameters for thsi
cn.Open "data source name", "userid", "password"
   Set cmd = Server.CreateObject("ADODB.Command")
   Set cmd.ActiveConnection = cn
   cmd.CommandText = "[dbo].[myproc]"
   cmd.CommandType = adCmdStoredProc
what will be value for second parameter for
   cmd.Parameters.Append cmd.CreateParameter("@mailid ",??what is the value ???, _
      adParamReturnValue)
   cmd.Parameters.Append cmd.CreateParameter("@user_guid",???adVarChar??, _
      adParamInput)
      cmd.Parameters.Append cmd.CreateParameter("@user_guid",,adVarChar, _
      adParamInput)
Please let me know