How to make a surface GUI that shows a humanoids health??

Hi, im trying to make a wall that has health (humanoid) and has a surface Gui on it showing how much health is left until the wall dies. I need to know how to make the Surface GUI work really. THANKS A TON!!

My script i wrote is as follows

repeat
script.Parent.CurHealth.Text = script.Parent.Parent.Parent.Parent.Humanoid.Health
until
script.Parent.Parent.Parent.Parent.Parent.Humanoid.Health = 0

the CurHealth Text is text inside a Surface GUI Label, and the script.Parent...Humanoid Health is the Humanoids health

The main problem is when the humanoid is damaged the Surface GUI should show the humanoids health. But it stays the same as i set it