function check_num(data) {   
  var my = '0123456789.';     
  var ok = 1; var checktemp;
  var i=0;
  if(data.charAt(0) == '-'){
  	i=1;
  }
  for (i; i<data.length; i++) {
    checktemp = "" + data.substring(i, i+1);
    if (my.indexOf(checktemp) == "-1") 
      return 0; 
  }
  return 1;
}

function add_thousands_seperator(data) {
  
  var Num = "" + parseInt(data);
  var neg = '';

  var temp1 = "";
  var temp2 = "";
  if (check_num(Num) == 0) {
    //alert("This does not appear to be a valid number.  Please try again.");
    alert(data);
    return "";
  }
  else { 
  	var count = 0;
  	var start = 0;
    if(data.charAt(0) == '-'){
    	neg = '-';
    	start =1;
    }
    for (var k = Num.length-1; k >= start; k--) {
      var oneChar = Num.charAt(k);
      if (count == 3) {
        temp1 += ",";
        temp1 += oneChar;
        count = 1;
        continue;
      }
     else {
       temp1 += oneChar;
       count ++;
     }
    }
    for (var k = temp1.length-1; k >= 0; k--) {
     var oneChar = temp1.charAt(k);
     temp2 += oneChar;
    }
    temp2 = neg + temp2;

    return temp2;
  }
}