Dynamic list box

Hi,
I have a requirement for the following:

In a text box, as a word is being typed the closest match is highlighted in a list box below.
So for example if I start to type

Lon ( for london )

the list below immediately goes to L when I type L, then Lo and so on till I finally rest on London.
I did ( with forum users help ) as similar thing involving dynamic list boxes with a 2D array in JavaScript. I presume this is much more involved.

I just need some pointers i.e.
Can it be done ( I am presuming yes ), major considerations ( time, effort etc ).

Thanks in advance.

Lenin.

Is the code for mine:

settime is my form name
Glist is my select list.
NewGuest is my textbox

Code:

---

function SearchGuest()
{
document.settime.Glist.options[0].selected = true;
var ListLength = document.settime.Glist.length;
var OptionContent='';
var NewContent = document.settime.NewGuest.value;
var ExitFun=false;

if(NewContent!=''){
        for(var x=1; x<ListLength;x++){
                OptionContent = document.settime.Glist.options[x].text;
                OptionContent = OptionContent.toLowerCase();
                if(OptionContent.substring(0,NewContent.length)==NewContent.toLowerCase()){
                        document.settime.Glist.options[x].selected = true;
                        ExitFun = true;
                        break;
                        }
                }
        }
}

---

put onkeyup="SearchGuest();" in your input text.