I'm stuck! Here's what I'm trying to do:

Vlookup($B$1,Named Range,$B$2,False)

This works, but there's more than one match for $B$1 in column A. I want to
sum the values in the column indicated in cell B2 if the data in column A
match the data in cell B1 --

Sumif(A:A,B1,[Column indicated in cell B2])

The problem is that the column with the values to be summed will change, so
a simple Sumif won't work. Thanks!