Debit note

Dear All,

I have a situation where we have few contractors doing works for our company for which we have issued them work orders, one of the contractor frequently uses our resources (machinery, vehicles and man power) with some excuses or the other, infact his work order value includes these costs which he now cleverly pass it on to us. Now i have already paid him 40% of the contact value and shortly in few days he would submit his next bill so before that i want to get your expert guidance for raising debit note for the cost we are bearing because of the contractor using our resources. Please give me the guidance and any sample format if any. Thanks in advance. 

Regards

Sree