Clearing documents in AP

Hi,

Just need advice on a special business scenario.

There are many invoices created which are open in AP.

Due to a special business requirement, all these have to be netoff against a write off account meaning, won't be paid.

There docs to set off basically credit memos are created using an upload Z program.

Now question remains like how do we clear these documets sinc all these are lying in open items.

there are so many vendors involved and hence manually doing one by one would take up most of the time.

is there any std clearing program or is there any method to clear these..?

pl advice.

thanx

neha