Adjusting Credit Memo

SOLVED

We handle all invoicing through the SO module.  I recently generated a credit memo through the RMA module.  However, the credit memo should not have been created.  I know I can do a debit memo to offset but I also know that that invoices and credit memos can be edited.  How is this done?  During my research it seems like it has to go through the A/R module and when I type the CM number I get a message that the CM number already exists and I click ok.  However, it does not prompt with a message asking me if I want to adjust the invoice.  


Is there really a way to modify a credit memo (or invoice) that is created through the SO module and not the AR module?