Here I am assuming that you have only three textbox which is not generating dynamically.
here is the html code :
<input type="text" id="Editbox1" onkeypress="MoveToNextBox(this, event)" maxlength="1" />
<input type="text" id="Editbox2" onkeypress="MoveToNextBox(this, event)" maxlength="1" />
<input type="text" id="Editbox3" maxlength="1" />
here is javascript code :
function MoveToNextBox(obj, event) {
var tab=new Array("Editbox1","Editbox2","Editbox3");
var id = obj.id;
var backSpace = event.keyCode;
if (backSpace != 8) {
if (id == tab[0]) {
document.getElementById(tab[1]).focus();
}
if (id == tab[1]) {
document.getElementById(tab[2]).focus();
}
}
}
Good luck.