DaniWeb IT Discussion Community - Help needed on select option (multible) [list box]

<html>
<head>
<title>Registration Page</title>
<script language="JavaScript">

function a()
{
document.f1.s2.remove(0);
}

function add(x)
{
var boxLength;
var selectedItem;
var selectedText;
var selectedValue;
var i;
var thisitem;
var isNew = true;

if ( x == 0)
{
boxLength = document.f1.s2.length;
selectedItem = document.f1.s1.selectedIndex;
selectedText = document.f1.s1.options[selectedItem].text;
selectedValue = document.f1.s1.options[selectedItem].value;
}

if ( x == 1)
{
boxLength = document.f1.s2.length;
selectedText = document.f1.t1.value;
}
//var newoption;
//document.f1.t1.value = x;//boxLength;

if (boxLength != 0)
{
for (i = 0; i < boxLength; i++)
{
if ( selectedText == document.f1.s2.options[i].text)
{
isNew = false;
break;
}
}
}

if (isNew == true)
{
document.f1.s2.options[boxLength] = new Option(selectedText,boxLength);
}
}

function rmv()
{
var selectedItem;
selectedItem = document.f1.s2.selectedIndex;
document.f1.s2.remove(selectedItem);
}

</script>

</head>
<body onLoad="a();">
<form name="f1">
Project : <br>
<select name="s1" size="5" multiple>
<option value="Project1">Project 1</option>
<option value="Project2">Project 2</option>
<option value="Project3">Project 3</option>
<option value="Project4">Project 4</option>
<option value="Project5">Project 5</option>
<option value="Project6">Project 6</option>
<option value="Project7">Project 7</option>
</select>

             
<input type="button" value="ADD" name="b1" onClick="add(0);">
             
             
             
             
<select name="s2" size="5" multiple>
<option value="P1">Project 1</option>
</select>
             
<input type="button" value="Remove" name="b3" onClick="rmv();">
<p>

New Project :
<input type="text" name="t1">
             
<input type="button" value="ADD" name="b2" onClick="add(1);">

</form>
<body>
</html>

The above work properly. But I have a problem with this code, that is -

When I select more than one Project at a time from the Project list and click on the add button at that time only one project selected and added into another list. I want to know how I able to add more than one project at a time from the Project list to another list. Please help me as quickly as possible.

Thanks & Regards,
Sabyasachi Banerjee.