Javascript paypal表单将下拉项的值添加到基本价格，并选中复选框

我正在设计一个贝宝表单，它的底价是2979美元。现在在我的表格中有复选框和下拉列表。可以选择多个复选框。选中复选框后，带有单个复选框的价格将添加到基本价格中。下拉列表也是如此

我的问题是我可以将复选框值添加到基本价格中，但下拉价格设置不正确。我想这是总数的两倍

请帮我解决这个问题

请在下面查找我的javascript代码和HTML代码：-

<SCRIPT type=text/javascript>
<!--
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 (".");
if (pos > 0) str = str.substring (rnd, pos + 3);
return str;
}


var validateDropdown=0;
var dropdownVal;
function validate()
{
validateDropdown=0;
var ddl = document.getElementById("DropDown");
var selectedValue = ddl.options[ddl.selectedIndex].value;
if (selectedValue != "Upgrade laptop")
   {
   validateDropdown=1;
   dropdownVal=selectedValue;
   }
else
  {
validateDropdown=0;
  }
}


function ReadForm (obj1, tst)
{ // process radio and checkbox
var i,j,amt=0,amt1=0,des="",obj,pos,val,tok,tag,finalamt=0,
 op1a="",op1b="",op2a="",op2b="",itmn="";
var ary = new Array ();
if (obj1.baseamt) amt  = obj1.baseamt.value*1.0;  // base amount
if (obj1.basedes) des  = obj1.basedes.value;  // base description
if (obj1.baseon0) op1a = obj1.baseon0.value;  // base options
if (obj1.baseos0) op1b = obj1.baseos0.value;
if (obj1.baseon1) op2a = obj1.baseon1.value;
if (obj1.baseos1) op2b = obj1.baseos1.value;
if (obj1.baseitn) itmn = obj1.baseitn.value;
validate();
for (i=0; i<obj1.length; i++)
{  // run entire form
obj = obj1.elements[i];        // a form element
if (obj.type == "checkbox" ||  // checkboxes
    obj.type == "radio")
{     //  and radios

//..................................................... one      set..............................................
      if (obj.checked)
    {           // did user check it?
    val = obj.value;           // the value of the selection
    ary = val.split (" ");          // break apart
        for (j=0; j<ary.length; j++)
        {  // look at all items
    // first we do single character tokens...
            if (ary[j].length < 2) continue;
            tok = ary[j].substring (0,1); // first character
            val = ary[j].substring (2);   // get data
            if (tok == "@") amt = val * 1.0;
            if (tok == "+") amt = amt + val*1.0;
            if (tok == "%") amt = amt + (amt * val/100.0);
            if (tok == "#")
             {             // record item number
                if (obj1.item_number) obj1.item_number.value = val;
                ary[j] = "";                // zap this array element
             }
        }


    val = ary.join (" ");           // rebuild val with what's left        tag = obj.name.substring (obj.name.length-2);  // get flag
    if      (tag == "1a") op1a = op1a + " " + val;
    else if (tag == "1b") op1b = op1b + " " + val;
    else if (tag == "2a") op2a = op2a + " " + val;
    else if (tag == "2b") op2b = op2b + " " + val;
    else if (tag == "3i") itmn = itmn + " " + val;
    else if (des.length == 0) des = val;
    else des = des + ", " + val;
  }
  //..................................................... one set..............................................

   //..................................................... one set..............................................
    if (validateDropdown==1)
    {           // did user check it?
    val = dropdownVal;        // the value of the selection
    ary = val.split (" ");          // break apart
        for (j=0; j<ary.length; j++)
        {  // look at all items
     // first we do single character tokens...
            if (ary[j].length < 2) continue;
            tok = ary[j].substring (0,1); // first character
            val = ary[j].substring (2);   // get data 
            if (tok == "@") amt = val * 1.0;
            if (tok == "+") amt = amt + val*1.0;
            if (tok == "%") amt = amt + (amt * val/100.0);
            if (tok == "#")
             {             // record item number
                if (obj1.item_number) obj1.item_number.value = val;
                ary[j] = "";                // zap this array element
             }
        }




  }

   //..................................................... one set..............................................
   }
  }


  // Now summarize stuff we just processed, above
  if (op1a.length > 0) obj1.on0.value = op1a;
  if (op1b.length > 0) obj1.os0.value = op1b;
  if (op2a.length > 0) obj1.on1.value = op2a;
  if (op2b.length > 0) obj1.os1.value = op2b;
  if (itmn.length > 0) obj1.item_number.value = itmn;
  obj1.item_name.value = des;
  obj1.amount.value = Dollar (amt);
  if (obj1.tot) obj1.tot.value = "$" + Dollar (amt);
 }
  //-->
 </SCRIPT>