Here's an idea to make this work: insert a row above or below your
revenue line (wherever it makes sense) and for each month in the new
row write a formula: IF(current month revenue is less than last month's
revenue,1,0). Then have your conditional formatting cell add up the 1
or 0 value in the new row for the current month plus the last two
months. Set the formatting to paint the cell yellow if that sum is 1,
orange if 2, red if 3. For aesthetic purposes, you can hide the newly
inserted row, or format the font to show up white on a white background
(not visible). Show it to your boss, so he/she will think you're a
genius, then leave early because it's Friday afternoon. Whoo hoo!