So you have nothing for your health bar yet?
The mouseover has nothing to do with a health bar i dont even know why you posted it.
This is how I would do a health bar:
sync on : `Turn updating on
sync rate 60 : `Set update rate
playerhealth=100 : `Starting health
do
CLS : `Clear the screen
ink rgb(200,0,0),0 : box 5,5,playerhealth,10 : `Display the health bar, always updated
if mouseclick()=1 then playerhealth=playerhealth-1 : `This is just a test to show you how to make the health go down
if playerhealth=0 then end : `Just showing you how to make the player die at the end after his health = 0, youd do something else but this is just an example
sync : `Update the screen
loop
Press left mousebutton to decrease health,
-inverted
PS: I commented it for a reason, dont just copy and paste it; learn how it works please
Come take a look!