How do I set up a smart contract?

I want to set up a smart contract that has the following parameters:

Contract begins when two parties fund it in an equal amount of at least $X

Contract ends on specified date

Contract pays totality of funds to one party if the condition is below a certain amount, and to the other party if the condition is above that amount

Condition is judged via a static government website that updates monthly

Is it possible to set up this smart contract myself? What service would I use to do that?