Jo90:
In addition to sourcing a file, if you're using korn/bash, you can use the autoload feature. Place these lines in /etc/profile, .profile, etc.
export FPATH=/usr/eds/functions # This is where autoloaded source resides
autoload function1 # alias for typeset -fu
Now, function1 isn't loaded until it's needed, and if you have a lot of other functions in the source file, they're never loaded unless required.
Regards,
Ed