data_1_1 = new Option("کرج","35");data_1_2 = new Option("تهران","2");data_1_3 = new Option("دماوند","32");data_1_4 = new Option("ساوجبلاغ","40");data_2_1 = new Option("مشهد","1");data_2_2 = new Option("قوچان","7");data_3_1 = new Option("زاهدان","6");    displaywhenempty="-- ابتدا استان را انتخاب كنيد --"
    valuewhenempty=-1

    displaywhennotempty="-- شهرستان را انتخاب كنيد --"
    valuewhennotempty=0


function change(currentbox)
{
   numb = currentbox.id.split("_");
   currentbox = numb[1];

   i=parseInt(currentbox)+1

   // I empty all combo boxes following the current one

   while ((eval("typeof(document.getElementById(\"combo_"+i+"\"))!='undefined'")) && (document.getElementById("combo_"+i)!=null))
   {
      son = document.getElementById("combo_"+i);
      // I empty all options except the first one (it isnt allowed)
      for (m=son.options.length-1;m>0;m--) son.options[m]=null;
      // I reset the first option
      son.options[0]=new Option(displaywhenempty,valuewhenempty)
      i=i+1
   }

   // now I create the string with the "base" name ("stringa"), ie. "data_1_0"
   // to which Ill add _0,_1,_2,_3 etc to obtain the name of the combo box to fill

    stringa="data"
    i=0
    while ((eval("typeof(document.getElementById(\"combo_"+i+"\"))!='undefined'")) && (document.getElementById("combo_"+i)!=null))
    {
       eval("stringa=stringa+'_'+document.getElementById(\"combo_"+i+"\").selectedIndex")
       if (i==currentbox) break;
       i=i+1
    }

   // filling the "son" combo (if exists)

   following=parseInt(currentbox)+1

   if ((eval("typeof(document.getElementById(\"combo_"+following+"\"))!='undefined'")) && (document.getElementById("combo_"+following)!=null))
   {
      son = document.getElementById("combo_"+following);
      stringa=stringa+"_"
      i=0
      while ((eval("typeof("+stringa+i+")!='undefined'")) || (i==0))
      {
         // if there are no options, I empty the first option of the "son" combo
         // otherwise I put "-select-" in it

         if ((i==0) && eval("typeof("+stringa+"0)=='undefined'"))
            if (eval("typeof("+stringa+"1)=='undefined'"))
               eval("son.options[0]=new Option(displaywhenempty,valuewhenempty)")
            else
               eval("son.options[0]=new Option(displaywhennotempty,valuewhennotempty)")
         else
            eval("son.options["+i+"]=new Option("+stringa+i+".text,"+stringa+i+".value)")
         i=i+1
      }
      //son.focus()
      i=1
      combostatus=""
      cstatus=stringa.split("_")
      while (cstatus[i]!=null)
      {
         combostatus=combostatus+cstatus[i]
         i=i+1
      }
      return combostatus;
   }
}