Changes

'''Step 3:''' You will need to go to the Edit view of the Dynamic Data - Dynamic Custom Control Field and create a new sub field. Create this 3rd custom field using type "Special - Browser Script" and paste the following script into the Javascript text box. Replace "xxxxx1" with the field id of the Dynamic Data - Dynamic Custom Field. Replace "xxxxx2" and "xxxxx3" with field id of all the fields that you need to sum up.