[TYPO3] Hiding not in rootLine n level menu items when n+1 level menu items are showing

[David Rennert]

Hello,

1. I implemented a HMENU with 4 root elements (we'll refer to them as level 
0 items).
2. When the user clicks a menu item it expends and shows all its child menu 
items (we'll refer to them as level 1 items).
3. When the user clicks one of the child elements it expends and shows its 
child elemtnes (we'll refer to them as level 2 items).
So far so good. Thing is - When the user performs action 3 above I want all 
level 1 elements, part from the one in the rootLine not to show.

How can I do that?