miscellaneous charge auto calculation for sales order.

commission charge for service provided on sales orders  are manually getting calculated. for example, if it's credit card payment.

we have an item called svc as a service item for credit card. sales clerk add a line to a sales order and manually calculate this commission fees onto the sales order.  There is a risk of human error of miscalculation of charge here.

 just  wondering if we could use the misc charge section to add the commission. Could this calculate this charge automatically on the invoice total.