Automatic Billing after sales order in SD for Non energy goods

Hi sap gurus,

i have a query it related to service order which is to be created and bill (OR ---F1)

the client requeire after careating a sales order the billing and invoice is trigger automatically and post invice in FICO.. As this process is not standard ..

please guide me what user exit i can use to trigger billing order from sales after saving ...

deepak mahle