Navitaire : How to change the Trip Availability Request

TripAvailabilityRequest availRequest = (TripAvailabilityRequest)this.SessionStore[SessionKey.TripAvailabilityRequest];
foreach (AvailabilityRequest request in availRequest.AvailabilityRequests)
{
request.BeginDate = DateTime.Now; //Changed Date

request.EndDate = DateTime.Now; //End date will be the same can change it
}

//Save it to the Existing session
this.SessionStore.Remove(SessionKey.TripAvailabilityRequest);
this.SessionStore.Add(SessionKey.TripAvailabilityRequest, availRequest);

Cheers ,