function searchfield(e)
{
var key;
var keychar;

if (window.event)
   key = window.event.keyCode;
else if (e)
   key = e.which;
else
   return true;
keychar = String.fromCharCode(key);
keychar = keychar.toLowerCase();

if ((key==null) || (key==0) || (key==8) || 
    (key==9) || (key==13) || (key==27) )
   return true;

else if ((("abcdefghijklmnopqrstuvwxyz 0123456789").indexOf(keychar) > -1))
   return true;
else
   return false;
}