Manually add fixed vertical horizontal line to chart

That is awesome, excellent and exactly what I'm after, many thanks!

On a side note, is there any way I can add labels to each quarter section? I've built a relationship model plotting data from accounting info and it places a service sector in one of the quaters, ergo:

Leverage, Strategic, Routine, Bottleneck. Just wondered if it would be possible to add a label into each quadrant on your chart?