Accessing datadir from bash (autotools)

Hello,

I have a project controlled with autotools. One of my executables is a
bash script (mybashfile) that must access a file (mydatafile) that was
put in a datadir with make install. My Makefile.am currently is:

bin_SCRIPTS = mybashfile
pkgdata_DATA = mydatafile

There any way I can know (from mybashfile) where mydatafile was
installed? Maybe I need to insert this information in mybashfile during
the "make", but how do I do it in Makefile.am?

Thank you in advance.

André