Here is the full thing, with support for max, min and decimal places:
Code:
Break ON
$=SetOption("Explicit","ON")
 
Dim $i,$r,$max,$min
$r=rng(0,0,@TICKS)
While "TRUE" AND Not KBHit()
	rng(10.00,20.99) ?
Loop
 
Function rng($iMin,$iMax,Optional $iSeed)
	Dim $vDiscard,$sDecimal,$i,$iFactor
	$sDecimal="."
	; Establish how many decimals to use
	If InStr($iMin,$sDecimal) $iFactor=Len($iMin)-InStrRev($iMin,$sDecimal) EndIf
	If InStr($iMax,$sDecimal) $i=Len($iMax)-InStrRev($iMax,$sDecimal) EndIf
	If $i>$iFactor $iFactor=$i EndIf
	$iFactor=CInt("1"+Left("000000",$iFactor))
	; Ensure min and max are in the right order
	If $iMax < $iMin $i=$iMin $iMin=$iMax $iMax=$i EndIf
	$iMax=$iMax * $iFactor
	$iMin=$iMin * $iFactor
	; Fix max to base (0)
	$iMax=($iMax-$iMin+1)
	If Not IsDeclared($_RNG_PERSISTENT) Global $_RNG_PERSISTENT EndIf
	If VarType($iSeed) $_RNG_PERSISTENT=CInt($iSeed) EndIf
	$_RNG_PERSISTENT=1103515245*$_RNG_PERSISTENT+12345
	; Emulate 16 bit shift right ($rng>>16)
	$rng=DecToHex($_RNG_PERSISTENT)
	$rng=SubStr($rng,2,Len($rng)-3)
	If $rng="" $rng=0 EndIf
	; Convert hex to Decimal and fix to scope
	; $vDiscard=Execute("$$rng=&"+$rng)
	$vDiscard=Execute("$$rng=CDbl(((&"+$rng+" mod "+$iMax+") + "+$iMin+")) / "+$iFactor)
EndFunction