Requisition Worksheet Issue

How do i use the Rescheduling Option of the ‘Action Message’ field in the Requisition Workshhet. Can any body help me in understanding the option with a scenario. Plz help in urgent.

When you run the requisition worksheet the “reschedule” message will be prompted to “suggest” you reschedule an order due to a movement in the demand. For example you planned to purchase on 06/10/07 but the system suggests you move this to 10/10/07. If you use the function to carry out the action message it will update it, although I recommend you tell teh vendor as well [:D]

Can u further help me on how to test the scenario with a case study. I am trying it on my part but was unable to receive the message. Plz help.