Thanks, I got it working now:
public void playEvent(EntityPlayer player, int code, BlockPos pos, int blockId) {
EntityPlayerSP realPlayer = Minecraft.getMinecraft().thePlayer;
if (code == 2001 && player == null && realPlayer != null
&& realPlayer.getDistanceSq(pos) < 46
&& realPlayer.rayTrace(4.5, 0).getBlockPos().equals(pos)
&& realPlayer.isSwingInProgress) { // 50 == 5 blocks (max. 4)
this.blockBroken = true;
}
}