Acessing functions across frames

[Brainz]

right... here goes. Let me know if this makes any sense.

I've got a frameset containing two frames:

<frameset cols=200,*>
<frame name=contents src=contents.htm>
<frame name=main src=indexmain.htm>
</frameset>

Contents.htm contains code culled from the Internet Explorer Tip of the Day (find it with the windows search: tip.htm), that shows or hides a subsection, contained in a <div>, when a user selects an anchor item in a list, using the style property display (is property the correct word?)
So, state as loaded:

o Item 1
o Item 2
o Item 3

User clicks item 2:

o Item 1
o Item 2
   o Item a
   o Item b
o Item 3

Then, user clicks item 3:

o Item 1
o Item 2
o Item 3
   o Item c
   o Item d

Each item is also a link with target=main.

All well and good, until someone clicks the back button. The Main frame goes to the previous page (that referenced by Item 2), but the contents frame stays in the same state, so the submenus no longer match.

What I want to know is if there is some way of calling the function in the document in the contents frame, using the onload event of the Main document's Body tag.