How to have Level 3 Superfish submenus stay on sub level pages

How to have Level 3 Superfish submenus stay on sub level pages

Hi,

I have created a vertical menu which works perfect on top level pages, however for sub level pages, I would like to have the parents visible. I tried adding class current to Level 2 which works fine, but I have not been able replicate it with level 3.

There are 2 images attached. dropdown image shows the standard hover effect of menus till level 3 which work fine and 3rd level nav shows what i want to achieve.

thanks,
joy