how does timing work?

The only reason you get a wrong answer on this forum is because you've asked the wrong question...mostly ;o)

Is this what you're after?

Type rectangle
	Field r, g, b
	Field x, y, w, h
End Type

Graphics 640, 480, 0, 2
SetBuffer BackBuffer()

r_count = 0

time = MilliSecs()

Repeat
	Cls
	
	; If times up, add a new rectangle to the list
	If (MilliSecs() - time) >= 1000
		If r_count < 20
			r.rectangle = New rectangle
			r\r = Rand(255)
			r\b = Rand(255)
			r\g = Rand(255)
			
			r\x = Rand(539)
			r\y = Rand(379)
			r\w = Rand(100)
			r\h = Rand(100)
			
			r_count = r_count + 1
			time = MilliSecs()
		EndIf
	EndIf
	
	; Draw all the rectangles in the list
	For r.rectangle = Each rectangle 
		Color r\r, r\b, r\g
		Rect r\x, r\y, r\w, r\h, 1
	Next
	
	Color 255, 255, 255
	Text 0, 0, CurrentTime$()
	
	Flip
Until KeyHit(1)

End

YAN