for(int day = 0; day < maxdays; day++)
{
List<int> mydays = new List<int>();
mydays.Add(day);
EvalEvent(0,day,mydays);
}

private void EvalEvent(int eventnum,
int day, List<int> mydays)
{
Parallel.For(day,maxdays, day2 =>
// events must be after previous events
{
   mydays.Add(day2);
   if(eventnum< eventcount - 1) // proceed to next event
   {
      EvalEvent(eventnum+1, day2,mydays);
   }
   else
   {
     EvalSolution(mydays);
   }
 });
}