Giving a mob an NBT tag while it's active

[ironkiller224]

I'm trying to give a mob the tag "NoAI". Is there any way to give it a tag using just the entity instance?

I attempted it this way:

public class voidCharmEffect {
	@SubscribeEvent(priority = EventPriority.NORMAL, receiveCanceled = true)
	public void onEvent(LivingUpdateEvent event){
		EntityLivingBase entitya = event.getEntityLiving();
		if(entitya instanceof EntityPlayer && entitya != null){
			EntityPlayer entity = (EntityPlayer) entitya;
			if(entity.getHeldItemOffhand().getItem() == ModItems.voidCharm  ){
				GameSettings gs = Minecraft.getMinecraft().gameSettings;
				RayTraceResult mop = Minecraft.getMinecraft().objectMouseOver;
				if(mop != null){
					if(mop.entityHit == null){
						
					}else{
						if(mop.entityHit instanceof EntityEnderman){
							EntityEnderman target = (EntityEnderman) mop.entityHit;
							//System.out.println("found enderman");
							target.getEntityData().setInteger("NoAI", 1);
							//System.out.println(target.getEntityData().toString());
						}
					}
				}
			}
		}
	}
}

It detects the mob but the mob keeps moving around.