Calculate Shown Fields Without Calculating Hidden Fields

I have a simple table with three columns and multiple rows. The columns are as follows:

1. Training Course Name
2. Checkbox
3.  Read Only field displaying the value of the training per hour. It also has a condition to hide until the corresponding checkbox is marked, i.e. $0.25

If an employee has completed a training they can check the box it will then show the value of the training.

At the bottom of the spreadsheet I am totaling the value of all the training they have completed with a simple calculated field: [Amount 1] + [Amount 2] + [Amount 3] + [Amount 4] + [Amount 5]

I was hoping that this formula would not count the value if the field is hidden, i.e. not checked. It does not however.

Any ideas how I would change my setup to get this to work?