QlikView App Dev

[anuradhaa]

I need to calculate avgrage time between 2 events

end time - start time

some events doesn't have endtime.

so what i want to do is display average time monthly.

i have select boxes and one box year, month

here i used end date for that.

what i want is display average time based on select month.

i have a event started on 2014 Nov and not finised,

if i select 2015 jan that event needs to get it end date as 2015 jan 31 as it's end date.

and if another record has it's end date on feb we needs to take that record and set it's enddate as 31st jan when we select 2015 jan.

please help me to do that,

attached qvw