I need a spreadsheet that will have several ranges of numbers on it that correlate number of staff needed to build per a required quanitity (i.e, 1ea widgetA = 2 staff, 5ea widgetA = 8 staff, 4ea widgetB = 3 staff, etc.)

I will go through and highlight the correct number of staff required per the current demand for each product. There are a large variety of widgets, so I want a cell that will add all the highlighted cells to give the total staff count required. How would I go about programming a cell to do this?

Thanks.