Summing up hours of different people for work orders

[Lucas_Cuypers]

Hi All,

How can i add hours of different people of the same work-order…
Sum(Hour((select(Working hours[Total],[Order] = [_THISROW].[Timestamp]))))

Total = duration
Order is the number of the workorder
the select is making a list of all total registrated hours on this order

but then i have a problem, i can not sum them up directly as it is not a number…
converting it to a number by using hours is not possible because it is a list…

any ideas…
thanks