Greetings Raghu,
Do you mean that the call should always be on the Wednesday (i.e. the Order is always created on the Wednesday, but the start date for the Order may actually be later - in which case please follow the advice above, and use the cycle length with the appropriate call horizon), or that the maintenance should always be scheduled to be due on the particular date (in which case please also follow the advice above to arrive at your solution; you may also have a look here http://sca.sap.com/message/14199025 for some ideas