BEX - subtraction of columns

Dear Experts,

I have in a requirement where 2 columns of stock values are displayed based on 2 dates given in the selection screen. Now I need to add a third column which should show the difference of the stock values and should be colored. is it possible to achieve in query level or do i need to go for custom exit.

Sample

1/1/2016 2/1/2016 Difference column (1/1/2016 minus 2/1/2016)

300 100

400 300

500 40

200 200