I have the following, in 4 different columns:

Col A Col B Col C Col D
Serial Type Serial Type
12345 0475 12345 0475
12345 4394 12345 4850
12345 9800 12345 9800
49302 1929 49302 0493
49302 8473 49302 8747

I need to determine if there are any types in Col D that are NOT in Col B,
for the same serial (i.e., also matching Col A and C). Columns A/B have
about 50,000 rows; Columns C/D have about 27,000. Is there a way to do this
quickly with some VB code? I'm at a loss here and have to get this done by
end of today. Thanks for any help......Paige