Here’s a quick and
easy way to copy an entry down a column. If you have numbers in B1:B5 that you
need to add to numbers in A1:A5, enter the formula =A1+B1 in C1. With C1
selected, double-click the bottom right corner of the cell. Excel copies the
formula down Column C until it sees an empty cell in Column B. Assuming B6 is
empty, Excel copies the formula into C2:C5.