Attaching documents to refunds

Hi,

Can anyone tell me if/how I can attach a document in my in-tray which is for a refund, to the relevant refund transaction?

If I cant tdo this via the in-tray, is there any other way I can attach the document to the refund transaction (it was a credit card transaction) so that I dont lose the information regarding the Credit Card refund?

Thank you in advance for your help,

Vicki