Anyone ever used the Order Cancellation Flat file to cancel multiple orders?

A brief background:

• AZ merged ASINs we were on, selling single FotL T-shirts, to a 5 pack listing.
• We sold 463 orders over night for 5 pack t-shirts for the price of 1 (5.75 instead of 23)
• After trying to get AZ to sort it themselves they have suggested that we cancel all orders via a flat file stating PricingError as the reason as we can appeal the inevitable negative metrics.

This is all fine and well, but the flat file asks for:
Order ID - 123-12345-12345
Reason - PricingError
AZ order item code - a 14 digit code

I have 3 issues is when I enter the 14 digit code into the spreadsheet:

1. It changes the format from 12345678901234 to 1.23456E+13 (Can I just amend the format?)
2. Some orders have multiple items in, therefore multiple AZ order item codes, yet I seem to only be able to enter 1 code? Am I OK to just enter 1 of the say 5 codes?
3. If there is a 0 at the start of the order code, it disappears. I know that if I put '0 it will stop this, but will this bugger the file up if the code has a ', thus making it a 15 digit code, not 14?

Is all the above simply an excel issue (I’ve never got on with excel personally), and could I stop all the issues by using something like openoffice?

Any help would be greatly appreciated.