Webi Date Prompt:Calendar Pick Doubt

Hi,
In the report we are using Start Date and End Date  as the Prompt, in the Date prompt we will be having the Calendar pick option. That Calendar pick will be always pointing to the current Date(If am no wrong.!!).
My Requirement is as follows..
If am selecting Start Date as 05/Jan/2012 and when i select the End date it should point to the month which i selected in the Start Date (i.e) Jan.
End Date should also point to Jan,
Similarly if i select Start Date as 12/Dec/2012, the End Date Prompt should point to the DEC-2012 instead of the Current Date.
Whether it can be done in BO.?
If yes how it can be achieved..!!!
 
 
Thanks
Arul N