__interface IWizardFinish : IUnknown
This interface is useful in advanced scenarios where you want to perform additional processing when you click Finish or Cancel in the UDI Wizard. The UDI Wizard contains a Finish task that saves task sequence variables when you click Finish. If you cancel the wizard, the task only sets the OSDSetupWizCancelled task sequence variable to TRUE and does not save changes to any other task sequence variables.
If you create your own finish component, you need to register it with code like this:
CreateInstance(pRegistry, ID_MyFinishTask, &pFinish);