Tony: ... really ? There's always a first time !
Anyhow, changing the EICAS layout should be necessary only for the first time, since you expect the program to save and recall that setting upon next startup.

By the way, I took the time to download the FSUIPC doc here at the office so that - despite the fact that I have no simulator here () I can point you to this particular FSUIPC command (and I'll do this for Jack's safe too ...).

From the keypress programming / button programming section of FSUIPC (accessible via FS2004 menu, "Modules" submenu) , after identifying the desidered key / button, simply use the drop-down command list, and point to
"PM GC controls (by param)"
with a parameter that ought to be (seen on page 35 of FSUIPC for Advanced Users.pdf):
20 to cycle the engine pages forward
21 to cycle the engine pages back

That's it.

Have fun, guys !
Eu