Any way to calculate the running total of values in a multi-insert field before actually inserting the form?

I have a multi-insert form that collects values for quantity, cost, and total cost (calculated value) for each row. I’d like to be able to provide my users a running total of the total costs so they know in real time how much the total order is based on the values they have entered thus far before actually submitting the form. Any suggestions on how I can go about this?