<script >

function Filter_Keyboard() {

var keycode = window.event.keyCode;

if( keycode >=37 && keycode <=40 ) return true;  // arrow left, up, right, down

if( keycode >=48 && keycode <=57 ) return true;  // key 0-9

if( keycode >=96 && keycode <=105 ) return true;  // numpad 0-9

if( keycode ==110 || keycode ==190  ) return true;  // dot

if( keycode ==8  ) return true;  // backspace

if( keycode ==9 ) return true;  // tab

if (keycode ==13) return true; // Enter

if( keycode ==45 ||  keycode ==46 || keycode ==35 || keycode ==36) return true;  // insert, del, end, home

return false;

}

function Sel_Year() {

}

</script>

<script >function Filter_Keyboard() {  var keycode = window.event.keyCode;  if( keycode >=37 && keycode <=40 ) return true;  // arrow left, up, right, down    if( keycode >=48 && keycode <=57 ) return true;  // key 0-9  if( keycode >=96 && keycode <=105 ) return true;  // numpad 0-9  if( keycode ==110 || keycode ==190  ) return true;  // dot  if( keycode ==8  ) return true;  // backspace  if( keycode ==9 ) return true;  // tab if (keycode ==13) return true; // Enter  if( keycode ==45 ||  keycode ==46 || keycode ==35 || keycode ==36) return true;  // insert, del, end, home  return false;}function Sel_Year() {
}</script>

=======================================

ตรง textBox

<input name=”txtMA” type=”text” id=”txtMA” onKeyDown=”return Filter_Keyboard();” size=”15″>