function trimSpaces(mytextbox)
{
   // elimina gli eventuali spazi in testa ed in coda alla stringa nella checkbox passata
   var len;
   var start, end;
   var mystring= mytextbox.value;
   var TrimmedStr;
   
   len= mystring.length;
   if (len==0) return;
      
   start=0;
   while( (mystring.charAt(start)==' ') && (start<=len-1) ) start++;
   if (start>=len) TrimmedStr="";
   else
   {   
      end= len-1;
      while( (mystring.charAt(end)==' ') && (end>0) ) end--;
      TrimmedStr= mystring.substring(start,end+1);
   }
   mytextbox.value= TrimmedStr;
   return;
}