dynamic selects

I have been doing some searching and looking on the forum for old topics
on the best way to change a select box based on another. So far, I have
only been able to get one way to work, and it only works in FireFox
(does nothing in I.E.)

I'm having a bit of trouble relating a lot of the examples out there
into what I am trying to do. Do I use the observe_field, or
onchange="<%= remote_function...
There are just too many ways. I was told about jQuery having a change
method that you pass a function to, but I failed to get that working as
well.

My issue is that I have 4 list boxes. You choose from the first one and
it populates the next two, then you select from the 3rd one and it
populates the last one. I have 4 objects; MachineType, Machine, Issue,
SubIssue.
The MachineType has_many :machines and :issues. The Issue has_many
:sub_issues.
I placed each select box into it's own div whose id's are the same as
the model names.

<div id="machine_type"> etc..

Is it better to use the options_from_collection_for_select helper, and
just type out the select tags, or should I use the select helper such as
f.select(:name)? Can anyone give me a good clear example on exactly how
to do this?

Thanks,

~Jeremy

here are a few of the links I checked out that didn't help me out.
http://www.roryhansen.ca/?p=9
http://www.bobbyvandersluis.com/articles/unobtrusivedynamicselect.php#a
http://lists.rubyonrails.org/pipermail/rails/2006-January/009728.html
http://www.adamhegedus.com/2006/01/19/ajaxed-select-boxes-in-rails/