It sounds like your application call needs to call an online
version of the help first and if this is not available to point to
a local copy. Is that right? If so, how this happens is entirely in
the hands of your developers. I know it can be done, just sketchy
on the actual procedure.
As far as the CSH in the help is concerned, you can use
mapids for both versions of the help if you want. If using webhelp
you'd do well to check out
this
link on Peter Grainge's site.