No. Some airline programs allow one-way redemptions, but many do not. Many programs will allow you to book a "stopover" with no additional mileage requirement. In this case you would be booking a roundtrip between New York and Athens with a stopover in Amsterdam. The rules for doing this, however, will be specific to the program and you will need to seek advice in the forum of the airline operating the program, which will not necessarily be the airline operating all (or any) of the flights. It's important to understand that most airlines are members of an alliance, and the miles can be redeemed for travel on any member of the same alliance (with occasional exceptions).

If this doesn't work out you could book a roundtrip with an "open-jaw" New York to Amsterdam, and Athens to New York should be redeemable. Then you might need to use the Worldpoints for the Amsterdam to Athens flights, but I would attempt the first approach first.