Sorry, I'm not fully up on the acronyms in use on this board so I don't know what MYW is. However, if you are talking about booking a room at one of the WDW resorts, I've found that it is much easier to have codes applied when I call. In fact, I'm not even sure if most of the codes can be applied when booking online.
That said, I have booked online to make sure I get the room I want and then later call to have a new code applied for a discount. That doesn't always work but at least that way I know my wide and I will be in a room we like. Also, talking to someone live about a reservation can sometimes let you know about any codes/discounts that you may not have heard about when booking online.
I do hope this helps. If not, at least it will bump your question up to the top.