If the 1500 numbers have the same prefix, that will be easy.
If the numbers are all very diferent, that will be dificult.
Example:
You wanted to block calls to a group of 1000 consecutive numbers:
Block 732 945-1000 to 732 945-2000.
On the hop off directory, make a entry
713 945-1* At the same time, apply a replacement that sends the calls to a number that does not exist, or provide a busy tone.
The call will not be “blocked”, the call will try to go out, but it will not reach the destination.
Not too elgant of a solution, but works.
Best luck.