basically i want to do this equation

if a1=a3 than w
if not check to see if a1=b3 than x
if not check to see if a1=c3 than y
if not check to see if a1=c4 than z

and so on.

can anyone tell me what function or functions i need to use to do this. i an
trying it with =IF and can't get it to work.