I have a sheet that looks like:
A B
a 1
b 2
c 3

=vlookup("a",A1:B3,2,0)=1
=vlookup("b",A1:B3,2,0)=2
=vlookup("c",A1:B3,2,0)=3

I want to add values {"a","b","c"}, so

=sum(vlookup({"a","b","c"},A1:B3,2,0))=sum({1,2,3} )=6