I'm new to Acrobat 5.05 and Javascript...

I have a simple issue/question:

There are 3 columns, QUANTITY, EACHES COST, LINE TOTAL

As the client enters a QUANTITY, the LINE TOTAL will update (QUANTITY x EACHES COST). This works fine via the 'Calculate Value is the product (x) of the following field' standard formula. Then I want to add the values in the LINE TOTAL column as the client enters or changes their order. This last step is where I'm having difficulties. Do I need to use Javascript? Or is there an easier solution? Please advise this newbie! Thanks...