I am curious that your lender had termite repair as a condition. That indicates you must have had a termite clearance as one of the conditions in your original offer.
Regardless, have your realtor contact escrow and ask them to generate an ammendment stating what you want to have happen. You will probably need to have the termite company present the invoice to escrow and you will need to bring the funds to escrow to pay for that up front. Once that invoice is with escrow they can generate the ammendment stating what will be done, when it will be done, and that you will be paying for it.
