Blocked invoices for posting to accounting due to service rendered date issue

Hi All,

We setup two cost keys (i.e. A01 and A02. A01 used last year and this year A02 and vice versa for following years).

Cost key A02 used this year and cost estimates completed. the issue is now, when ever creating Credit Memo reference to delivery from last year. when try to release to accounting, its giving error to check for last year cost key but if keep blank service rendered date in Credit memo its checking for current cost estimates and released But again if i do this pricing conditions changed and impacting on price also.

Any suggestion to avoid updating settings in KE40 every time if we stuck this kind of documents.

Thanks ind advance.