Yammer Custom Share Button to External Link

Question

I need to create a share button on Yammer to share an external URL from whare the OG infomation will be extracted. I´m using the example MS gives in the share button docs.

     var options = {
            customButton : true, 
            classSelector: 'share-yammer-button',
            defaultMessage: 'My custom message', 
            pageUrl: 'http://the-url-for-og-information'
        }; 
        yam.platform.yammerShare(options);

I need to post that to an specific group, but there´s nothing on the documentation about that.

Did anyone face the same problem?