Look at 'Documents To Go' in the App Store. I'm a Numbers user, so I've not used this particular app, but it claims to be able to sort. Remember, too, that if an app doesn't do what you want, Apple will always refund the purchase price as a credit to your iTunes account. Just call the Apple Support line with the transaction reference number from your iTunes invoice.
Good Luck. I'm sure other Members will be able to help, too.
Tim