I have two separate worksheets with lists of accounts. Some accounts are on
both worksheets, and some accounts exist only on one worksheet.

My goal is to create a third worksheet with a master list of accounts that
also sums the values of any accounts that appear on both worksheets.

Would this involve summing VLOOKUPs, or is there a quicker way of pasting
both lists onto the third worksheet and then summing dupes?