Would anyone have an idea of how to sum values based on a lookup.

eg.

- List 1 -
Col A Col B
b 2
d 4
e 1
x 3
y 2


List 2
a
b
c
d
e

What I need to do is add selected List 1 Col B values where List 1 Col
A values appear in List 2. So the result above would be 7.

Is there some array formula so I don't have to do a lengthy nested
SUMIF for approx 30 values it needs to look for in List 2.

I know I could insert another column with a VLOOKUP to return
something and then SUMIF on that return value, but it's for an
existing large spreadsheet and I 'd rather do it in a single formula
if possible.

Many thanks

Peter