Anyone know how to make gantt chart reflect task on hold days?

On the tasks page, I’d like to be able to omit “on hold” days from the total time logged on a given task, and to have that reflected in the gantt chart (so two bars on one line).

Does anyone know how to do this? I have a date column called “hold date” and another called “resume date” and a formula column that tells me how many days a task was on hold. I can tell the duration column to subtract the hold formula column to solve my count, but it doesn’t make the gantt chart reflect the situation.