Project: Magento Inventory Update

We have a php script that will update our product inventory from a csv file directly into the mysql database via sql, using the product SKU as identification to update. However we want to update the inventory by a custom attribute field instead of SKU e.g. supplier_sku. We also want to update other custom attributes as well as the standard qty, is_in_stock etc... We have the basic code that we want to work from with samples of csv data to insert. This job needs doing ASAP