parameters in script

[mar_zim]

hi to all good day.
how can i pass a parameter in a function?
what i want is i just want to pass a parameter in a function and call the function on my onkeypress of textbox.
i have this code and it seems won't work.
pls. help im very new in this thing..

<form>
    <input type="textbox" name="textbox1" id="txttel" onkeypress="keydown(event,'txtname')">
    <input type="textbox" id="txtname" onkeypress="keydown(event,'txtadd')">
    <p>
    <input type="textbox" id="txtadd" onkeypress="keydown(event,'txthome')">
    <p>
    <input type="textbox" id="txthome" >
    </form>
<script>
    document.getElementById("txttel").focus();
</script>
<script>
    function keydown(e,var s){
    if (!e) var e = window.event;
    if (e.keyCode) code = e.keyCode;
    else if (e.which) code = e.which;
    if (code==13){
    document.getElementById("s").focus();
    }
    }
</script> 

thanks in advance guys..more power.