javascript Grid list with key up and down

Java Script Code

function inkey(event,count){
count = parseFloat(count) -1;
var existing = parseFloat(document.getElementById("id").value);
var add = parseFloat(document.getElementById("id").value) + 1;
var minus = parseFloat(document.getElementById("id").value) - 1;
if(event.keyCode == 40){
document.getElementById("id").value = add;
if(existing == count){
document.getElementById("id").value = 0;
}
document.getElementById("botx" + document.getElementById("id").value).click();
}
if(event.keyCode == 38){
document.getElementById("id").value = minus;

if(existing == 0){
document.getElementById("id").value = count;
}
document.getElementById("botx" + document.getElementById("id").value).click();
}
}