Hi Fubar,
Thanks for your reply. I'd already done most of this but, just to be sure, I tried again but it's still not showing.
I double-checked my code in the function by having it in the Form Step and calling it from within the $(document).ready(function () { code. When the code is in the Form Step, it works - when it's removed from the Form Step and added to the Web File, it doesn't work.
I also thought it could've been the way the functions were being declared in the file, they had been in there as var FunctionName = function (fieldName) { so I tried changing them to function FunctionName(fieldName) { but this didn't affect anything.
The one thing I've forgotten to do previously was to sync the changes - I tried this but, as with all of the above, still not working.
I also tried, on the Web File, to change the Parent Page. I'd previously got it set to the Multistep Form and tried it on the Home page as well but, as before, this didn't work.
The fallback position of having a copy on each of the Form Steps isn't the end of the world so I'll look at doing this. I think I've spent enough time trying to get this working.