Double line on the bottom border of a cell
I am a CPA and I want to use Numbers for all of my spreadsheet work in my office. However, I cannot because I need to be able to use a double underline as the bottom border for a total at the end of a column of numbers - footing at the bottom of a column. This is a common need of all accountants. I know how to do this to double underline text, but cannot see how to do this for the bottom border of a cell. Any ideas on how this can be done very simply and in a professional looking manner? Thanks!
MacBook Pro (Retina, 13-inch, Mid 2014), OS X Yosemite (10.10.5)