stop duplicate item description through personalization

Hi,

I am using oracle apps r12

I am using trigger when validate record on mtl_system items with the following condition

:MTL_SYSTEM_ITEMS.DESCRIPTION_MIR=(SELECT DISTINCT DESCRIPTION FROM MTL_SYSTEM_ITEMS_B WHERE :MTL_SYSTEM_ITEMS.DESCRIPTION_MIR =DESCRIPTION) and

:SYSTEM.RECORD_STATUS in ('NEW','INSERT')

and in the action I am using RAISE_FORM_TRIGGER_FAILURE and shows the error message.

It works fine and it is stopping to create duplicate item description.

But when I try to update an item it is stopping to do that as well.

So I want a personalization to stop duplicate item description only when I create new item description and not on the update the item.