Input data on sales invoice

Hi,
can anyone help me please,when i input an item in the sales invoice,each item needs to be related with a slaughter fees.
Example:
when i input Beef as an item ,the value for slaughter fees (21.60)should appear automatically in the table.
and when i input sheep as an item ,the value for slaughter fees(14.50) should appear in the table.
so can you tell me how to make this?

Regards,
Trishty