No, you got something completely wrong.
A double-spend is two transactions sending the same coins to two different
addresses. Only one of the two transactions can possibly be accepted as valid, and as soon as one of them is confirmed, the other one becomes invalid. And if the now invalid transaction was payment for goods or services that you already delivered without waiting for confirmation of the transaction, you just got ripped off. There is no way to know, short of waiting for confirmations, whether a double-spend has taken place or is about to take place.