am I right, that it then has only to run without errors and the tex code is not important, it is invisible to the outside LyX world??
Sorry, but I don't understand what you are asking. If you are asking, "will I, the user, be able to see what latex I'm using?", then the answer is a definite "YES!".
No, I meant if it is important what kind of LaTeX code you are using for your purpose: should it be an elegant LaTeX wise code or a short code, which isn't very nice, but does what you want, checking only (for internal use of LyX) if a file exists or not, which is only:
[EMAIL PROTECTED]
\renewcommand{\include}[1]{%
[EMAIL PROTECTED]@warnNotFound{#1}}%
}this is not elegant, because you have a double check for the existence of the file, but it does what you want ...
Herbert
