Expense Booking against a Customer Service Order

Dear Sir,

We have a following scenario :

A Customer has placed a service order for the repairing of a machine and on receipt of customer order , we have created an order in SAP using VA01 . To render the desired service , we may have to put some components and technical skill etc for repairing the machine . We need to monitor all expense incurred for executing the reference order . Once the machine is repaired , a Service Invoice (in reference of customer created sale order) shall be raised .

Our query is that how can be book the expenses against the reference customer order . Request the forum members to kindly guide on this please .

With Rgds

B Mittal