function mobile_message_char_counter(form_object, chars_max) {
   var amount_chars = form_object.value.length;
   if (amount_chars > chars_max ) {
     form_object.value = form_object.value.substring(0, chars_max);
     chars_left = 0;
   } else {
     chars_left = chars_max - amount_chars;
   }
   document.getElementById(form_object.id+'_counter').value = chars_left;
 }