求教，一個試很久都不行的 store proc 的問題！(編號：7003)

舉一個例：
CREATE PROCEDURE ORDERbyPNNO
@pnno char (8) ='%'
AS
set nocount on
SELECT　XXXXXXXXXXXXXXX
FROM ORDERA INNER JOIN
CUST_A ON ORDERA.O_C_id = CUST_A.C_ID

WHERE (ORDERA.O_PNNO LIKE @pnno　)
set cn =new adodb.connection
cn.open "XXXXXXXXXXXXXXXXXxx"
Set rspnno = New adodb.Recordset
rspnno.CursorLocation = adUseClient
rspnno.Open "orderbypnno %", cn, adOpenDynamic, adLockOptimistic, adCmdStoredProc
為什麼這樣查不到東西呢？ 這樣查，出現語法錯誤，把 % 拿掉，又會出現 @PNNO 這個變數是空的！
請教高手，怎麼樣才可以出把參數帶進@pnno中呢？謝謝