There is nothing in USPAP that says you can't do that specifically, but you have to answer the question of what data do you have and what is the reliability and relevance of that data. I assume that since you are asking this question, you are in desparate straits for ANY comparables.
If that is the case, look for similarity in design and appeal, to the greatest extent possible. Look at sales in your own development up to two years old or like Randolph said, listings pendings, etc. Examine if there are any expired or withdrawns in your development over the past year. Those can be a great indicator of the ballpark of where you might be, value wise. When you exhaust all those otions, then look outside your development to competing developments. Even ones that may be somewhat distant. Don't forget to address differences in location. Compare any sale over any time period from your development to a sale at the same time period that is detached, and that percentage difference can give you an approx. adjustment amount.
And above all....explain, explain, explain.