Can be used in any Sales Transaction with **Sales Team** Table:

    
    
    cur_frm.cscript.custom_validate = function(doc) {
        // calculate incentives for each person on the deal
        total_incentive = 0
        $.each(wn.model.get("Sales Team", {parent:doc.name}), function(i, d) {
    
            // calculate incentive
            var incentive_percent = 2;
            if(doc.grand_total > 400) incentive_percent = 4;
    
            // actual incentive
            d.incentives = flt(doc.grand_total) * incentive_percent / 100;
            total_incentive += flt(d.incentives)
        });
    
        doc.total_incentive = total_incentive;
    }