window.open

I have written a menu in java script where the link takes you to a web address code as follows:
var MENU_ITEMS =[
[“Sports & Leisure”, null,
[“Bowling clubs”, “bowling”],
[“Sports clubs”, “sportsclubs”],
[“Sports centres”, window.open(“http://www.wirral.gov.uk/ed/sports_centres.htm”, “target” ) ],
[“Parks”, “http://www.wirral.gov.uk/er/”],
[“Libraries”, “http://www.wirral-libraries.net/” ]

],
I would like the window to open when the link is clicked and not when the index page is loaded of the site. How do I over come the problem?

Cheers