[Exim] executing scripts in alias files?

Hey all!

I have a couple of scripts for use with emails. For example a script that
takes an email address as parameter and sends an email to the address
saying, that he got an email (for use with SMS)...

Does anyone know how I could include this in an Exim alias file, so that
ie. for the alias joe, joe gets his email and a script is executed?

ie.
joe    joe,"some_executed_script with_a_parameter"

thanks,

philipp