C-S-E Function Help

Please can someone tell me if this is possible:-

I am starting to use the CSE function as explained in a past tip of the week and it is working well but I want to know if it can be expanded.

eg.
Column A : <Location List> North, South, East, West South.etc
Column B : <Salesman> John, Jim
Column C : <Sales figure > 10, 20, 50 etc

At the moment if i want to get the sum of figures for South Region i am using the following CSE:
=sum(if(a1:a10=A30,c1:c10)) &LT;a30 being"South">

Is there a way to get a value for the Southern Region with the name Jim at the side? I have tried the following but it comes up with the wrong answer:

=sum(if(a1:a10=a30,and(b1:b10=b30),c1:10))
&LT;where b30="Jim">

Thanks for any help...