function autoTab(input,len) {
if(input.value.length >= len)
input.form[(getIndex(input)+1)].focus();
}

function getIndex(input) {
var index = -1, i = 0;
while (i < input.form.length && index == -1)
if (input.form[i] == input)index = i;
else i++;
return index;
}