Method to return date value.

Hi ,
    I have to create a method, which has two parameter, the parameter one is WeekNo and parameter two is year. I want to return date of the first day of the week.
for eg,
if WeekNo is 2 and year is 2009 then date should be 08/01/2009.
 I need some effective way to achive this functionality.
 
Regards,
Bala.
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