How to exclude a directory from PATH when searching an executable ?

[Timothy Madden]

Hello

On my particular system at work we have to install a dubious program 
called CUBRID, and the package they provide for it also installs its own 
version of bison and puts that directory on the system PATH.

So now my configure scripts (and all other scripts and consoles for that 
matter) use bison from CUBRID instead of the version installed on the 
system.

Is there a (portable) way to express in my configure.ac that I want to 
check for and use the bison executable, but I am willing to accept the 
executable found in /usr/share/cubrid/bin/bison only if there is no 
other bison found on PATH or on the system ?

Thank you,
Timothy Madden