Tweening + Delay on high FPS

Hello,

I have found a good tweening code that i changed a bit to count both UPS (Updates Per Second) and (Frames Per Second)
With this code, the engine always runs at a fixed game logic rate, so it is very handy!
Now, what else i want todo is cap the FPS if w exceed the UPS. Meening, If the UPS 35, we should never allow more then +-35FPS. If the UPS is 50, we should not allow more then +-50FPS.
Currently, my logic runs nice at 50UPS, because i fixed it. However, FPS runs over 120 FPS eating CPU.
As you can see i tried to delay (to save CPU) and reduce the FPS back to 50, but it works not as i hoped. Because it will toggle between 120FPS 50FPS 120FPS 50 FPS, etc... (which is logical :P)
I smell that i should do it timebased, but i dont yet really see how i can achieve that.

Graphics 800, 600,, , GRAPHICS_BACKBUFFER

Global UPDATE_FREQUENCY:Int = 50
Global update_time:Float = 1000 / UPDATE_FREQUENCY
Global t:Int, dt:Int
Global execution_time:Float = 0

t = MilliSecs() 
While Not KeyDown(KEY_ESCAPE) 
	dt = MilliSecs() - t
	t = MilliSecs() 
	execution_time:+dt
 
    While execution_time >= update_time
		'UPS.Update()
		'Update()
		execution_time:- update_time
	Wend
	
	'FPS.Update() 
	'Render(execution_time / update_time) 

	rem
	If FPS.count > 0 And UPS.count > 0 And FPS.count > UPS.count
		Delay(Float(FPS.count) / Float(UPS.count) * 10) 
	End If
	endrem
Wend