How to make javascript only take effect once per browser session

[se_p800]

Ok bare with me i am new to html. I posted a similar thread but realised I was asking the wrong thing so I thought it best to start again.

The javascript I am using is called modalbox. In order for it to work you have to add the neccessary files to your server and paste this code into your pages:

<link rel="stylesheet" href="popup/modalbox.css" type="text/css" media="screen" />
<script type="text/javascript" src="popup/prototype.js"></script>
<script type="text/javascript" src="popup/scriptaculous.js?load=effects"></script>
<script type="text/javascript" src="popup/modalbox.js"></script>

I have got everything working fine except I only want this script to take effect once per browser session as shown here

I have tried adding this after the code:

<script type="text/javascript">
submitTags : function()
{
var btnSubmitTags = document.getElementById( TagsHelperConfig.FORM_TAGS_ENTRY_SUBMIT_BUTTON_ID );


btnSubmitTags.click();
}
</script>

As from what I can tell from the source code on the website I just listed that is what they have used, but I am having no luck. Is anybody able to modify the code I have pasted to make it only take effect once per browser session? If so I would be so appreciative. Thanks