Why not create a name called "pct," which equals c14/(c$14:c$25). Then the formula to use in cell N14 is simply "=pct". You can copy and paste that to all other cells C15 through C25.
You want to show percent of what? Percent of the total expenses? Give us a simple example of what you're trying to do so we can help. But if that's all you need then the percentage of each expense...