Yikes.. I didn't realize that..
Okay.. I did try calling the function using your syntax above:
document.f1.alloy.onChange();
which came back with an error.
I also tried calling the function and passing in a value as Glenngv suggested but also had no luck:
alloyselected(document.f1.alloy);
I feel like a damn moron.. Obviously I'm looking for a non-browser specific answer. The way I got the previous IE only function to call was to put it in the onLoad handler so each time the page is refreshed it will automatically do it.. and that seemed to work fine.
I'm baffled and frustrated (as I'm sure you are with my babbling

)..