Sorry for the newbie questions here:

VMS is the X client.
A Macintosh is the X-display.

The MAC has a different keyboard/mouse environment.

For instance, on VMS, with the really neat patch that was provided some
time ago, the mouse thumbwheel acts as up/down arrow keys.

On the MAC, the thumbwheel acts as its own button (and it has both
up/down and left/right).

And obviously, there is the issue of the backspace (works fine in
decterm, but not in TPU).

Here is the context: I use the Mac as the X-server/display/terminal. I
have a DECW$DISPLAY logical on the VMS host that points to the Mac. I
start individual applications without having a decw$login or decw$session.

(eg: use RSH to do a CREATE/TERMINAL and from then, can run various X
applications including TPU etc).

In such a context, would keymaps on VMS still be used, or would it be
soley the keymaps on the Mac that would be checked ?

Is it possible to tell the VMS apps to consider the mouse thumbwheel as
arrow keys ?

AKA: I don't want to change the Mac's X keymapping because it would
interfere with existing Mac X applications.

Or is the only way to achieve this to change the kaymappings on the Mac
and affect all Mac (X) applications ?

And if the keymappings need to be changed, what info do I need from XEV,
and where to I put it ?