though there may be a better way of doing this, depending on the layout...
I've named the cell with Net Sales Total in "NetSales"
Row 1 formula =IF(NetSales>14000,14000,NetSales)
Row 2 formula =IF(NetSales<=14000,"",IF(NetSales>=18000,4000,NetSales-14000))
Row 3 formula =IF(NetSales<=18000,"",IF(NetSales>=22000,4000,NetSales-18000))
Row 4 formula =IF(NetSales<=22000,"",NetSales-22000)
Note also that it may be better to have the various thresholds in cells and have the formula refer to those cells... that way any changes can be made to the cells not the formula.
I suspect a lookup table may be the best way of approaching this really, but it's difficult to preguess any other variables that may be involved.
However, I think what I've done above will work if you just need it quickly.