How to automatic post the profit OR loss to short term Capital / long term

Hi,

How to automatic post the profit OR loss to Short term Capital gain / Long term capital gain on posting of Sales transaction ?

Incase the inventory item is less than one year older then the difference should be posted to the G/L of Short term Capital gain, where as if the item is more than one year older then the difference should be posted to the G/L of Long term Capital gain

Thanks in advance

Samir Gandhi