title: Advanced Excel Formula
body: <p>I have an Excel spreadsheet with 25,168 rows. Each row represents a customer with a unique customer number and dollar amount. One customer may appear in this list up to 31 different times on 31 different rows. If I were to sort this list based on our Customer ID number, A2-A24 might be customer number 123, A25-A33 might be customer 479, and so on.</p>
  
  <p>I want to create a formula that generates a total of the amounts in each row for all rows containing the same customer ID number. For example, if Customer ID Number 123 appears in rows A2-A5, and the dollar amounts associated with these rows are B2=$1, B3=$2, B4=$3, and B5=$4, I want the formula to sum B2-B4 for Customer ID Number 123, which is obviously 10 (1+2+3+4).</p>