I know it is possible to do but could not find how

Did you try a Gooogle seach for say 'javascript copy to clipboard'. This only works in IE 5+ AFAIK.

<form name="myForm">
<input type="text" name="someText">
<input type="Submit" 
onclick="window.clipboardData.setData('Text', someText.value); 
alert(window.clipboardData.getData('Text')+' -> clipboard');">
</form>
<script>myForm.someText.focus</script>
[download]