Probably an easy answer but i cant figure it out for anything

I want to show a "summed total" data label for a stacked column chart.

For example, i am looking at sales tax revenues. The years are broken out on the bottom of the chart (x axis). i have 4 data series, which are broken down by quarters (Q1,Q2,Q3,Q4).

Now, i want to show visually the difference in the quarters, but have a data label showing the "summed total" for the entire year.

any help is much appreciated.

thanks in advance,
greg