为何出错"不正常的定义参数对象。提供了不一致的或不完整的信息"

Dim Z_DB As ADODB.Command
Set Z_DB = New ADODB.Command
Z_DB.ActiveConnection = Z_LocalMachine_ODBC
Z_DB.CommandType = adCmdStoredProc
Z_DB.CommandText = "PROC_zquan_test"            '后台存储过程名,肯定没有错误
Set paraM1 = Z_DB.CreateParameter("@tablename", adVarChar, adParamInput, 20, "T200")                 '输入的参数a
Z_DB.Parameters.Append paraM1     '参数1
Set paraM2 = Z_DB.CreateParameter("@colname", adVarChar, adParamInput, 20, "TFCL")                 '输入的参数a
Z_DB.Parameters.Append paraM2     '参数2
Set paraM3 = Z_DB.CreateParameter("@numname", adVarChar, adParamInput, 20, "1")                 '输入的参数a
Z_DB.Parameters.Append paraM3     '参数3
Set paraM4 = Z_DB.CreateParameter("@colvalue", adVarChar, adParamInput, 20, "2")                 '输入的参数a
Z_DB.Parameters.Append paraM4     '参数4
Set paraM5 = Z_DB.CreateParameter("@num", adVarChar, adParamOutput)            '返回的参数
Z_DB.Parameters.Append paraM5        '这儿报错"不正常的定义参数对象。提供了不一致的或不完整的信息"
Z_DB.Execute
MsgBox Z_DB.Parameters("@num"), 48, "ddddd"
Set Z_DB = Nothing