Need to get a Count with Multiple Conditions

Hello,





In Tab # 2 I have a column that has different "sites" in Tab 3 I have a count of all the computers at the different sites and then another column of what the computer is a desktop or laptop. I need on Tab 2 to look at the site on Tab # 3 (that matches what I am trying to get a count on on Tab 2-and could have several rows) and look at the site and then give me a count of all the desktops.
So Tab 2
A=Site
B=Count of Computers
C=Desktop ?
D=Laptop?

tab 3
A=Site
B=Laptop or Desktop

Thanks
Christine