Update purchase rate

Update purchase rate

Hi There,

We run a consignment business and use Zoho Inventory to manage all our stock.

We would like to set a custom function to automatically update the purchase rate of a product depending on the Vendor Comission rate which is a custom field we have created per product.

i.e Update Purchase Rate to 40% of sales rate

Can I get some help with this... I was hoping that I would be able to simple use field update, however the fields available don't match our needs.