How can I show up and down arrows when a value changes?

[Julie]

I'm creating a financial spreadsheet on comparison of year-to-year and
month-to-month sales. If the sales go up from previous year, I want to show
an up arrow beside it and if it goes down, down arrow. How can I achieve
this? Can I make it an automatic thing for instance if the number is postive,
it's an up arrow and negative down arrow?

 

[Eduardo]

Hi,
Highlight the column, do conditional formating, icon sets, choose the arrows