Task End Trigger New Task

A lot of times you are working with tasks such that when one task is completed you want another task to be started. In MS Outlook, what if those guys created a system where a task is 'alive' only when another task is completed. So I complete task A, and now I must begin task B, and task B is autocreated in the task list.

It's kindda like a Gantt Chart but in outlook or Kontact or Lightening.