MaskedEdit ReadOnly from javascript

Hi,

We are using MaskedEdit control from AjaxToolkit.

We have a requirement of making this control ReadOnly from javascript.

I tried setting readOnly attribute of text box from javascript but it doesn't work.For normal text box without mask it works.

I need to achieve this using javascript only ,after page is fully rendered.

Also i dont want to disable text box because of its styling.

Any help will be appreciated.