Excel formula bar default font

It's hard to see a leading negative sign on the Excel formula bar. For example, if I want a formula to be =-A1+B2 (instead of =B2-A1) the default font makes it easy to miss.

How can I change the font of the Excel formula bar in Office 2013. Note this linked answer does not work for me because I have no Office Button. I am using Office 2013 on Windows 7.

Second but rhetorical question: why is the default font completely unsuitable for formulas in Excel and this stackexchange website?