hiding visual app notifications?

I desperately want to be able to turn off visual notifications of a certain app on my BB (what's app).
I have noticed on the iphone there are options to turn off all notifications for this app so you only know of knew messages when you physically go into the app, but I cant see anything like this on Blackberry (Bold 9780).
Does anyone know anyway of doing this??
I've heard something about creating a theme to hide certain visual notifications?? Is that right and how would I get this done?

Hope someone can help
Thanks