I'm not at all clear what it is you are attempting to do... exactly. but it sounds like it is something that needs pretty exact settings. There are certainly ways to setup and control your external devices separately. And there are certainly ways you can take a FILE with you and load that into your rented Motif XS. But the devil's in the details.

In order to control separate devices with separate pedals would require you go beyond just the standard cc11 and cc7 messages, and program at least one of your external devices to respond with VOLUME change to a non-Fixed function Control Change message... like cc04.

For example, if you send cc7 or 11 from a master controller everything on the channel will respond (or ignore) the messages as a change in volume.
You may need to control one of your external devices with a message like Foot Control cc004 assigned directly to its internal level control.

So even if we give you what to do on the Motif XS you will still need to program some things to respond on your external devices. You will want to learn about the Motif XS MASTER mode, this is where you can define regions and controllers to specific MIDI Channels.

Thanks for your reply. I'm sorry I wasn't clear.
It sounds like the Master mode might be what I'm looking for but I will try to explain a little more for clarity.

I would like the keyboard, mod wheel, pitchblende, sustain pedal etc to transmit on the global channel e.g. ch1.
I would like the first expression pedal to transmit on the same global channel (ch1) and midi cc 04.
I would like the second expression pedal to transmit on midi channel 15 and midi cc 11.

The important bit is the second expression pedal transmitting on a different midi channel.

Briefly, I am using this to control a Cubase setup for live performance. Every song has a fresh project, with the midi filtered or remapped to control various soft synths and their functions. These are programmed for each project.
You don't need to know this so feel free to skip this, but in case you're familiar with Cubase ...The problem occurs because Cubase can assign a midi input to be the default controller for its generic editor (e.g. to control transport, faders, mutes, vsti's) globally for all projects. I also need the same controller (on the Motif) to control Cubase's Track Quick Controls, which are programmable for each project. For the two pedals to operate correctly as either a Quick controller OR Generic Editor controller they must appear on different midi channels.

I hope this helps ...it's actually a very simple thing I'm trying to do. Most decent midi controller keyboards will allow their knobs and pedals to be assigned whatever channels and cc numbers I choose. It just seems that the Motif's complexity as a workstation doesn't make this easy to find.

Thanks again, and any help how to do this precisely would be appreciated. In the meantime I'll take a look at Master mode in the manual!

You'd rather download the PDF reference manual and have it read thoroughly or, better, buy a Motif XF...