[Lizard]

Each resource can only have 1 cost/hour. So you'd have to set up extra resources at the new billing rates "Joe -- time and a half" and "Joe -- double time" and set their schedules to only be one day each. Then you'd have to coordinate scheduling tasks between the 3 different Joes. You could probably make it work, but OmniPlan doesn't really have proper support for this.