In that case you can also look at Ad-Hoc workflows or Review Workflows.
Search for workflows labelled "adhoc" for examples, WS45301171 has an example of both.
All three are equally valid solutions, it depends on your needs on how tightly integrated it needs to be. In order of integration:
- Making it a part of the decision (as per Stephane's solution) is permanently hard-linked for everyone.
- Ad-hoc workflow inserts it into the WF (visible in the graphical log), but needs an explicit action by user to do so
- Review workflow is more of a 'soft' link, can be initiated by the approver, and is not part of the graphical log. Still recorded in the technical log.
- Mail is completely open to all and not part of the log.
Regards,
Mike