Formula for working out Employer National Insurance contributions

I use the following formula to work out an employers National Insurance contribution, =SUM(Q174-162)*13.8%. Q174 being the wages cell, 162 is the threshold over which employers NI is paid at the rate of 13.8%. The formula works however when I copy the sheet from 1 week to another the formula displays a negative value. In addition if an employee doesn’t earn that week again their cell is set to a negative value. Is there a more sophisticated formula that would set the cell to zero value if there were no entries in the wages column for that employee. Thanks in anticipation

Thank you very much for that. It worked a treat