SSRS dynamically changing of calendar parameters

Hi. In a SSRS 2008 report with two calendar parameters StartDate and EndDate I try to corelate these parameters in a followig manner: 

1. If I set the StartDate>EndDate, automatically the StartDate value must get the EndDate value. Otherwise the StartDate value remain at selected value

2. If I set the EndDate<StartDate, automatically the EndDate value must get the StartDate value. Otherwise the EndDate value remain at selected value.

These values of StartDate and EndDate parameters must change accordingly by previous conditions I want.

How can I implement this logic ?

Thank you.