Have you looked at the new (18.1) Gantt chart type?
Might the Percent Graph column item type be useful to you? If nothing else the markup techniques of Percent Graph and Time Axis may give some ideas for a custom item plug-in or it may even be possible with a HTML Expression type column.
I think it should be possible to do something similar to what I see in the two JET Cookbook time axis examples. I would need to know more about exactly what you are trying to achieve.
Hmm, I see what you mean, John. I am actually using the Gantt chart, as it does display exactly what I want...maybe I need to re-think how to do what I want to do. I basically want to have interactive grid rows that match up with the Gantt chart rows, so that the data associated with each row can be easily edited while viewing the corresponding Gantt data at the same time. Any suggestions for the easiest way to do this? I was looking at jamming Gantt into IG because I love the functionality of IG.