Visual Help: Line chart, with legend, and a dynamic constant line

Hi All,

Im after a way, to display a Line chart, with a legend, AND have said line chart always be able to plot a single constant line (which is dynamic/data driven).

Our scenario,

We need to display SLA % passed, by month, dissected by priority.
We also have a requirement for the SLA Target (say 90%) to be displayed as say a red line/shaded area/whatever, so we can see that the sla's by priority are clearly falling below target.

A Line and clustered column chart kind of gets me there - but the visual for it isnt what the business wants.

Making the column stacks as the sla then the target the line plot does plot what i need, but does a poor job of showing up/down slided between months, a line does this better than a column.

In this case:

- our X axis is month

- Our plotted value is SLA %

- Our legend is priority (so each priority's sla is plotted as a separate line).

The line chart (nor any chart it seems) allows me to plot multiple values AND have a legend. It seems to be one way or the other.

Does anyone know of a work around, or a marketplace visual that may help?

I've also considered doing this as KPI, but this wont behave correctly either, as i cant get the sla/priority plot split on a single graph to happen.

A sample of what im after, where the green line is a constant line coming from a datasource (measure). I added the line in myself to illustrate the sample.

Thanks,

Andrew