How do I detect blocks of a certain type near an entity?

In a mod I am developing I have a block called the Ender Suppressor that will stop all Ender Teleportation within ten blocks of itself (don't worry, it will need an Enter Pearl every half-hour, so it is balanced!).

So anyway, I have tried lots of ways to make this work. Here is what I tried: 

In the TileEntityEnderSuppressor class have an ArrayList<EnderTeleportEvent>and whenever an Ender Teleport event is detected it will add that to the list. In the update function of the TileEntity it will iterate through the events list and check if each one should be cancelled, but it doesn't work. I think the reason could be that the block is trying to cancel the event after it has already happened.

So what I want is to do this (psudeo-code): 

function enderTelrportEvent(EnderTeleportEvent event) {

    Block[] enderSuppressors = world.getBlocksWithinAABB(BlockEnderSuppressor.class, event.getEntity().getBoundingBox.expand([some amount]));

    if (length(enderSuppressors) > 0) {

        event.cancel();

    }

}

Also, if you can think of any other solutions please tell me.

P.S. After I have fixed this problem I will properly announce the mod and the other content in it.