Disable past dates in Date Navigator

Hi All,

Can any one let me know how to disable past dates in a Date Navigator UI element in Web Dynpro for ABAP?

For example,today's date is 21-May-2010,when i open my application, i want all the dates from 1 May to 20th May to be disabled.The user should not be able to select them.

Any help would be greatly appreciated,

Thanks,

Salma