Try this array formula:
You will need to extend the range down as far as you data. Since this is an
array you will need to press Shift+Ctrl+Enter to enter it.
It is not at all clear why you are multiplying by 24, since you are looking
at dates, when you subtract two date that are 3 days apart, Excel return the
number 3, which you are multiplying by 24 for a difference of 72 days (not
If this helps, please click the Yes button.