adding to different totals dependant upon selection from drop down
 

I have a drop down box that has three selections in it, and, dependant upon
which department in the drop down box is selected, then the following amount
in the next two following cells is added to a different departments total.
eg, if i select W formthe drop down box then dpeartment w's totals for labour
and parts is added to from two cells, Any help or assistance is greatly
received
Thank you
Shaun