Sorry for the terribly worded title, but here's what I want to do:

 

When a player is standing near a blood altar with <potion effect> then <thing happens>.

I have the code to do this, but I don't know how I would do this.

 

 

Check if the player has the specific potion effect or is standing by the block. If they are, then do something.

The potion will be a custom potion I add, yes.

 

And I already have the code:

  List<EntityPlayer> list = SpellHelper.getPlayersInRange(worldObj, xCoord + 0.5, yCoord + 0.5, zCoord + 0.5, 15, 15);
//                for (EntityPlayer player : list)
//                {
//                    PotionEffect regenEffect = player.getActivePotionEffect(Potion.regeneration);
//                    if (regenEffect != null && regenEffect.getAmplifier() > 0)
//                    {
//                    	if(AlchemicalWizardry.causeHungerChatMessage && !player.isPotionActive(Potion.hunger.id))
//                    	{
//                        	player.addChatComponentMessage(new ChatComponentText(StatCollector.translateToLocal("message.altar.hunger")));
//                    	}
//                        player.addPotionEffect(new PotionEffect(Potion.hunger.id, 40, regenEffect.getAmplifier() * 2 - 2));
//                    }
//                }

(Ignore that it is commented out)

That is what (used to be) there, and I want to replicate what I am doing, but instead of causing hunger it will fill the altar, slowly.

 

I already know how I will do this bit though. I just need to know how to "inject" my bit of code into the class file for the Blood Altar (which is a tile entity).

 

i.e. Blood Altar's tile entity file, which is where this code goes, will load with my bit of code added in.