Develop a smart contract for real estate transactions using BTC or other cryptocurrency

I need a smart contract for BTC or another crypto, to be developed for a real estate program. Here are the background requirements and functionality I need: EF Crypto Realty Outline 2.20.21 Someone wishes to buy a house using BTC or other crypto, and the seller wishes to sell their house and receive cash Buyer and seller agree on a cash price (fixed value for the house) The buyer places their crypto into escrow The smart contract (to be developed as the goal of this project) serves to pay out to the buyer the difference between the original agreed purchase price and further price rises in the value of the crypto paid for the house. Here's an example to illustrate what I need: A house seller and buyer agree on a cash price for the house, say USD $100,000 in this example. The buyer places into escrow the value of $110,000 in cryptocurrency, which is 10% more than the agreed sale price. This extra 10% is designated as a realty commission payment. The escrow liquidates $100,000 and sends it in the form of cash (not crypto) to the seller. The seller is satisfied and their side of the transaction is entirely completed. The buyer now owns the house. At the same time, the smart contract controls the remaining $10,000 (retained initially as commission). During the months following the completed sales, if the value of the underlying cryptocurrency rises in the global marketplace, then the smart contract will send disbursements to the home owner in the amount of the rise in value of that cryptocurrency beyond the date of the house sale. Continuing in the same example as above: The buyer purchases the house for $100,000 and in the months following the house sale, assume the value of the underlying crypto rises so that the crypto used to purchase the house “would have been” $150,000. In this case, the smart contract is designed to remit the difference of $40,000 to the buyer. In other words, the smart contract must be designed so that it allows the buyer who uses cryptocurrency to participate in further upward price moves of the underlying currency that he used to buy the house. Of course, if the value of the underlying currency falls after the house purchase, then the buyer retains ownership of the house, yet he wouldn't receive any further cash disbursements from the transaction, until/unless the value of the crypto used to buy the house would rise upward beyond the initial value of that crypto at the time of the original sale.