Help optimizing this simple calculator (also help with a function)

I’m trying to build a simple calculator it on

When the check box is clicked the desired value shows but it doesn’t get added in the to the field “Total Deductions” thus to “Approximate Net Proceeds to Seller” as well.

And I’m sure I don’t have an optimized code. I’m sure I’m doing things redundant and maybe this is also costing memory a lot more than it should. Thanks for all your help in advance. :slight_smile:

Edit: also if the check box is unchecked the value doesn’t turn to zero again. :frowning: