I have a spreadsheet that lists various order numbers on multiple rows
with different amounts for that order. I want to create a new "Order
Total" column and create a formula that adds all the amounts for each
order number that is the same. So looking at the table below, order
number 11111 will have a value of 175 (100 + 50 + 25 = 175) in the
Order Total column for each row where the order number is 11111.

I hope I'm clear. It can be difficult to put this stuff into words.
=)

Thanks
David

(new column)
Order Number Amount Order Total
11111 100 175
11111 50 175
22222 25 375
11111 25 175
33333 100 250
22222 250 375
33333 150 250
22222 100 375