function limitCharsTo(myfield, e, patt, opts, enterKeyPosts) {
   var key,keychar;
   var pattern;

   if (patt==null||patt=='') {pattern=/[0-9a-z]/i}
   else {pattern=new RegExp(patt,opts)}

   if (window.event)
      key = window.event.keyCode
   else if (e)
      key = e.which
   else
      return true;

   keychar=String.fromCharCode(key); //convert to string

   // control keys
   if (key==13&&(enterKeyPosts==null||enterKeyPosts=='')) {
      return handleEnter(myfield,e);
      }

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

   return pattern.test(keychar);
   }