You'll need to create an HTML link and write a Javascript that will respond to the onclick event and do the job. The link can be added as an HTML cell on the form. The Javascript will roughly need to do the following:
1) Access the value of the URL's stored in the text attribute. To do this use the following code:
var form = AwareApp.getFormPanel (this).getForm ();
var urls = form.findField ('AttributeName').getValue ();
where AttributeName is the name of the attribute that stores the URL's
2) Parse the contents of the string and split it into substrings for each URL. You can use standard methods of the String object to do this
3) For each URL you can use Java script functions to open a window for the given URL