[Keep It Simple Stupid]

I have created a form (that will be filled out differently every time). The
form is protected.
Within the form, there is a table with 3 columns:
Unit Price - Quantity - Total
I need the Total column to automatically calculate (UnitPrice X Quantity)

There is a form field in the first two columns for the user to enter
numbers.

I have tried putting a form field in the Total Columns as a calculation
(=A2*B2), but it only calculates the first time. In other words, if I "blank
out"or change the number in the Quantity column or the Unit Price, the total
doesn't update.

How can I get this to work?