Jon,
There is not something like this specific but per my last comment for your other post, if you use the workflows from within the Notification Manager Apps from the Marketplace (http://www.clarizen.com/appsmarketplace.html), you can adjust the closest workflow (notify resource) and use that customization to Assign a Resource to a Task with a future Start date. The workflow would have logic that would send the notification when $StartDate is a certain amount of time prior to the Start date (i.e. 3 days).
For further clarification, we suggest you register for one of our daily Q&A webinars (see the link-> http://www.clarizen.com/resources/online-demo.html#second ).These are great resources for free consulting with our Customer Success Managers and visual answers to your questions.
Sincerely,
Boris