highlighting duplicate data,in a column across all cells

I have a large compilation of data on an excel work sheet (I am using 2013). All cells relate to each other by means of dates, names, and other numeric values such as stock numbers, id numbers etc... In one column some stock numbers are repeated. I would like to know if there is a way to set up the program on this worksheet to highlight all repeating stock numbers, not only in the column but across the cells as well, in lieu of doing so manually.
Thank you for your help.

Welcome It's always better to attach a sample file.

What I would do is to first sort the range by stock number and then color the entirerow - see the simple macro in the attached file.