Measure on the date different

Hi,

I had a huge file of aroiund 10 000 line.
This 10 000 line only consist of 500 items.
I wish to have an analyise a information.
Example
in the file it have items, order date, recept date and qty.
Item A order 3 time on 1 Jan but recept 1 time on 1 Feb and 2 time on 15 Feb.
Item A order 2 time on 1 Feb but recept i time on 1 Mar and 1 time on 15 Mar
etc for Item B......
Ans
Item A 2 time take 30 days and 3 time 45 days.
The numbers of days can be range 25 to 30 act as 30 and 40 to 50 can act as
45.
etc for Item B .......