Keyboard navigation for TREE Menu

[Maxi]

I have a webpage with 6 frames, one of the frame on the left side has a
Javascript TREE menu. I want to navigate the tree menu with keyboard. I
know the keyboard keys (It uses SPACEBAR to expand and collapse) but
the problem is when I use the TAB key to go to that frame and then use
the SPACEBAR, it does not expand. I have to click on any of the TREE
menu option and then keyboard navigation works fine but then TAB does
not work to go to the next frame.

In short, it gets Focus when one of the TREE menu option is clicked by
mouse and then it does not loses focus on any key pressed. I have to
come out of it by clicking on any other area of Internet Explorer.

Help.