You are asking here for "embedding one language into another", which, as @Bayou already explained, is not supported directly. Maybe you were spoiled from the HTML-world, where you can squeeze CSS and Javascript in between and maybe use some server side PHP or Ruby stuff too.
The closest to this are HERE-documents. If you write inside your bash script a
csh <<CSH_END
your ...
csh ....
commands ...
go here ...
CSH_END
these commands are executed in a child process driven by csh. It works the other way around with bash in the same way. Make sure that the terminator symbol (CSH_END in my example) starts in column 1.
Whether this will work for your application, I can't say, because things which run in the same process in your original script, now run in different processes.