Tweening help

Hey peeps... ive created a general tween function, but it doesnt work its best...
Now, ive played and played and played, and tweening has always done my head in, this function was like a godsend when i created it...

This is just the "include".
instead of "renderworld:flip", call "Renderworldtween(frames per second)

Can anyone help fix this so that it is actually the same speed on everyones computer?

Cheers

Damien

Global rendertweenskipframes#,oldrendertime#

Function RenderWorldTween(fps#)
Local tween#,Beforerender#,Afterrender#,tw#,framespd#,renderspd#,afps#,TWEENVAL#
If rendertweenskipframes>1 Then rendertweenskipframes=0
If rendertweenskipframes>0.99999999999 Then rendertweenskipframes#=rendertweenskipframes#-1:Goto skiprendertween
tween#=0
Repeat
	If tween#=0 Then beforerender=oldrendertime
	TWEENVAL#=TWEEN#
	
	;If tween#>1 Then Goto Dontrenderthisbit
	If rendertweenskipframes<1 Then tweenVAL#=tween#+rendertweenskipframes:rendertweenskipframes=0
	om=MilliSecs()
	;If tweenval=0 Then
	RenderWorld tweenVAL#

	If debugtext=1 Then
		;----------------------------------------------------------------------------
		;---PLACE DEBUG AND DRAWING STUFF HERE----
		;-----Note, 2D stuff will NOT be tweened for obvious----
		;-----reasons													    ----
		;---------------------------------------------------------------------------
	EndIf

	Flip 0
	If tween#=0 Then
		afterrender=MilliSecs()
		renderspd#=afterrender-beforerender:framespd#=1000.0/fps#
		tw#=renderspd#/framespd#
		If tw#<.000001 Then tw#=1
		If tw>5 Then tw=5   ;To stop endless loops
	EndIf
	DebugLog tween#+"  "+tw#
	tween#=tween#+tw#
	If twEEN>1 Then rendertweenskipframes#=rendertweenskipframes#+TWEEN#-1
	
	.Dontrenderthisbit
Until tween#>=1
.skiprendertween
CaptureWorld
oldrendertime#=MilliSecs()
End Function