var order = new Object(); // object to store order items in
var root = new Object(); // selection criteria
var on = true;
var off = false;
var cntr = 0; // items in object
var opts = 5; // number of options to allow
var tamt=0,tqty=0; // totals

// place for user-specific options
root.xx_can = ""; // place for PayPal cancel return path
root.xx_cur = ""; // enter default currency code (or null)
root.xx_id = ""; // PayPal ID
root.xx_img = ""; // image URL
root.xx_lc = ""; // enter default country code (or null)
root.xx_ret = ""; // place for PayPal return path
root.xx_sty = ""; // place for PayPal page style
root.xx_xtra = ""; // place for other PayPal commands

function CalcRoot () { // calc root stuff
if (root.shp) spos=0; 
if (root.tax) tpos=0;
}

function DispTots () { // display totals on the page
var tmp,d;
  d = document.orderf;
  d.sub.value = Dollar (tamt);
  d.tot.value = Dollar (tamt);
}

function Dollar (val) {     // force to valid dollar amount
var str,pos,rnd=0;
  if (val < .995) rnd = 1;  // for old Netscape browsers
  str = escape (val*1.0 + 0.005001 + rnd);  // float, round, escape
  pos = str.indexOf (".");  // should be one, but OK if not
  if (pos > 0) str = str.substring (rnd, pos + 3);
  return str;               // return valid string
}

function GetOrder (id, des, amt) {  // get all ordered items
var i,nr,val,qty,pos;
var op = new Array ();    // accumulate options here
  tamt=0,tqty=0;   // zero totals
  nr = id.substring (2);  // get number part of ID
  qty = document.orderf["qty" + nr].value;  // get qty
  if (isNaN (qty)) {      // test entry
    alert ("That is not a valid number!  Try again.");
    return;
  }
  for (i=1; i<=opts; i++) {     // see if any options
    if (document.orderf["op" + i + nr]) {
      val = document.orderf["op" + i + nr].value;  // get option
      op[i] = val;
      pos  = val.indexOf ("@");       // price set?
      if (pos >= 0) amt = amt + val.substring (pos + 1)*1.0;
      pos  = val.indexOf ("+"); // price increment?
      if (pos > 0) amt = amt + val.substring (pos + 1)*1.0;
      pos  = val.indexOf ("%"); // percent change?
      if (pos > 0) amt = amt + (amt * val.substring (pos + 1)/100.0);
    }
    else op[i] = "";
  }
  document.orderf["prc" + nr].value = Dollar (qty * amt);
  if (cntr == 0) order = new Object (); // zap object
  cntr = cntr + 1;               // bump counter so no zap next time
  order[id] = new Object ();     // create new entry
  for (i=1; i<=opts; i++)        // load options
    if (op[i] != "") des = des + ", OP" + i + "=" + op[i];
  order[id].des = des;           // load up values
  order[id].amt = Dollar (amt);
  order[id].qty = qty;
  for (i in order) {             // calc totals we might use
    qty = order[i].qty*1.0;
    tamt = tamt + order[i].amt * qty;  // total amount
    tqty = tqty + qty;                 // total quantity
  }
  DispTots ();                         // calc totals
}

function SendCart () {  // send the cart to PayPal
var frst = true;  // 1st pass thru items.
var winpar = "width=710,height=390,scrollbars," +
             "location,resizable,status";
var strn   = "https://www.paypal.com/cgi-bin/webscr?cmd=_cart" +
             "&upload=1" +
             "&business=" + root.xx_id + root.xx_xtra;
var i,j=0,des;
  if (root.xx_cur.length > 0)
    strn = strn + "&currency_code=" + root.xx_cur;
  if (root.xx_lc.length > 0)
    strn = strn + "&lc=" + root.xx_lc;
  if (root.xx_can.length > 0)
    strn = strn + "&cancel_return=" + root.xx_can;
  if (root.xx_ret.length > 0)
    strn = strn + "&return=" + root.xx_ret;
  if (root.xx_sty.length > 0)
    strn = strn + "&page_style=" + root.xx_sty;
  if (root.xx_img.length > 0)
    strn = strn + "&image_url=" + root.xx_img;
  for (i in order) {  // send all valid data
    if (order[i].qty > 0) {
      j = j + 1;
      des = order[i].des;
      strn = strn + "&item_name_"    + j + "=" + escape (des) +
                    "&item_number_"  + j + "=" + i +
                    "&quantity_"     + j + "=" + order[i].qty +
                    "&amount_"       + j + "=" + order[i].amt;
      frst = false;
    }
  }
  if (j > 0) window.open (strn, "paypal", winpar);
}

<!-- hide from validators
//  site set-list - things to set as options
// place for user-specific options
  root.xx_can  = "";   // place for PayPal cancel return path
  root.xx_cur  = "USD";// enter default currency code (or null)
  root.xx_id   = "yoga@clearspringstudio.com";  // PayPal ID
  root.xx_img  = "";   // place for image url
  root.xx_lc   = "US"; // enter default country code (or null)
  root.xx_ret  = "";   // place for PayPal return path
  root.xx_sty  = "";   // place for PayPal page style
  root.xx_xtra = "&rm=0"; // place for other PayPal commands
  CalcRoot ();       // calculate values. (required entry)
//-->