Cancel Save event of My Task Page

I have a PDP page in project server 2013 on premise and on it have added My Task Web part. I have to perform my custom validation on Task JSGrid . When user clicks on Save button and if Task Grid validation fails then needs to cancel the save event.

I am using the solution mention under below post to hook into the save event and show my custom validation messages on Save button click.

http://blogs.msdn.com/b/husainzgh/archive/2011/08/01/hooking-into-the-project-detail-page-ribbon-save-button-without-overriding-out-of-box-functionality-in-project-web-access-for-project-server-2010.aspx

The issue is, I am not able to cancel save event in this solution if validation fails?

Please help !!