Dropdown list options/Auto-filtering?

In my spreadsheet, I have some columns where the cell values are either Yes or No. When I enter No, I enter it as a Bold Red font.

Is there any way to do this automatically so I don't have to always change the font style and color each time I enter a new "No" value? Like with a dropdown list or with auto-filtering?

Thanks. So I used conditional formatting to create some rules to make certain values bold and a red font (as opposed to highlighting the cell in red), but it doesn't allow me to also change the font size. Is this not possible in Excel 2007? There is a font size section, but it's grayed out and won't let me select anything.