Adding a trendline to chart

Hi guys,

I have a bar graph here with 4 bars on it. basically what i want to do id to add a vertical line to the graph so that it seperates the 4 bars into 2 sections.
i just need it to be a fine dashed line.

i kno i could add a dummy series to my data and get it to graph the line that way but is there a nicer way to get the same effect?

cheers for your time!!

You could use gridlines if you set the number of categories between ticklabels to 2.