Google Analytics Tracking Event Code Doesn't Work With Button

Hi,

I’m trying to use Google Analytics to track events when users click on the button. How do I add the code correctly? I tried this but it doesn’t work.

[button href="http://testing.com" rel="nofollow" target="_blank" onClick="ga('send', 'event', { eventCategory: 'affiliate', eventAction: 'vendorname'});" css_classes="button_hilite _button"]Get More Details[/button]