Discuss "Change TextBox input language" in the JavaScript Programming forum.

<%
function ChkStr(strT)
	strT = Replace(strT, "a", "α")
	strT = Replace(strT, "b", "β")
	ChkStr = strT
End Function
%>

<input type="text"
id="test" onKeyUp="ChkStr(this.id)">

function greeklish(x)
{
var y=document.getElementById(x).value;
y=y.replace("a", "α");
y=y.replace("b", "β");
y=y.replace("g", "γ");
document.getElementById(x).value=y
}


<input type="text"
id="greek" onKeyUp="greeklish(this.id)">

function change_letter(id){
  var txt = document.getElementById(id).value;
  var old_txt = '';
  var new_txt = '';
     for(var i=txt.length-1;i<txt.length;i++){
         old_txt = txt.charCodeAt(i);
         //chr ref for a=97 for z=123 isNaN takes care of any other key presses
            if(old_txt>=97&&old_txt<=123&&!isNaN(old_txt)){
               //difference in chr numbers between a and alpha is 848
               new_txt = String.fromCharCode(txt.charCodeAt(i)+848);
               //replace the old character for the new one
               document.getElementById(id).value = txt.replace(String.fromCharCode(old_txt), new_txt);
            }
     }
}
 

<input type="text" id="textbox1" onkeyup="change_letter(this.id)" /> 

if (y.match("c")) 
{
alert("Μόνο ελληνικά");
y=y.replace("c", "");
}