Cancelling Transactions uploaded from a thirdparty

 Dear All,We are having a big challenge. Invoices from a third party software were uploaded in the system. Then user found out that the invoices were duplicated. So credit memo was made for all the invoices(700+) and uploaded again to the system. When the autoinvoice was run, the credit memo is captured four times in the in each customer's account. We need to delete these (700x4) four credit memo transactions.

Please help.

Thanks in advance for your help.

Vitalis