[Exim] System filter - Macro variables

I'm currently using some parts of the "Generic Windows Executable Content filter" from ftp://ftp.exim.org/pub/filter/
with Exim 4.04.

This filter definies the file type inside a regular expression four times. The only items, which are differ, is the
start and the end sequence of these regular expressions. The file types inside the regular expressions are always the
same, therefore is there a way to put these file types in a macro similiar to the macros in the configuration file.

Thanks in advance

Swen