@simbed there currently isn't a way to do automated calculations at this moment in time but I'll put in a feature request on your behalf.
In the meantime, a possible solution could be to add a signoff to the step that requires the calculation. The person who does the signoff could subtract the numbers and either approve or reject it. Another option could be to set a minimum and maximum in the data capture form. A worker could then do the calculation and enter the value, if it doesn't match the criteria, they won't be allowed to continue.
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