How can I create event on planned order

[pavankasulabada@pcmc.com]

Hello Workflow Gurus ,
                                         How can I create a event when a
new planned order is created .I have checked change documents , LIS ,Status
etc,.The only thing I can see is creating through function module .But
where should I use it .As we know that planned orders were created when MRP
runs .
 
Thanks
Pavan Kumar kasulabada