3 list box updates

[NoMAd]

I have three list boxes running in the one form..
I want it to run so once I select something from the first list box it updates the second, and then click the second and it updates the third.
The first box displays products types..
CPU
Motherboard
etc...

The second I want to display product names that are in stock of that type...
The query im running is for the second box is:

select name
from product
where type=Forms.<formname>!<[list4]>

and ive set that to requery when the first boz is clicked, yet it doesnt work, can someone help?

thanks..