Data series label in Stacked Chart
 

Let me explain by an example:

I am making a Stacked Chart for 1st Quarter of Sales from dffierent Staff

Month Staff Sales
Jan A 100
Jan B 200
Feb A 400
Mar C 100
Mar D 600

Staff B has record in Jan only. When I choose to show the data series on the
Stacked Chart, the name of B appear on Feb and Mar also at 0 level. I want
the name of Staff B Data series label only appear in Jan.

How can the chart show the data series label which has data(sales) only?