"context sensitive" layout

[Simon Bailey]

hi all,

is there any way i can set a variable globally and react in the
layout/header block depending on the content of the variable?

i have the following files:

marschbuch.ly
concert.ly
trbnI.ly
trbnII.ly
trbnIII.ly
trbnIV.ly

trbnI - trbnIV each contain a \book block with numerous pieces (at the
moment 17 and counting) -- which explains why i don't want to have to
create these files for both layout types...

marschbuch.ly creates a5-landscape with 16pt staves; concert.ly
creates a4 portrait with 20pt staves.

for layouting the 15-landscape version, i've had to force a few
breakbefores in the \header, but these are not needed in the a4
portrait version.

i'm thinking i could define a boolean variable in the marschbuch.ly
and concert.ly files, and then set breakbefore accordingly. but i have
no idea how. can anyone help?

thanks, regards,
simon.
--
Do not meddle in the affairs of trombonists, for they are subtle and
quick to anger.