Ian,
Probably it is best not to use a report for this. If it's going to a
text file, then it is almost certainly going to be better to base your
export on the query that the report is based on. If I am worng about
this, please post back with more information about what you are trying
to achieve.
The macro action to use is the TransferText action. By default, this
will export to a comma delimited text file with ""s around the text
format data. If you want something other than the default output, you
can control it by running through the process manually via the
File|Export menu, and at the final screen of the export wizard, click
the Advanced button, and save your definition as a Specification, which
can then be entered into the SpecificationName argument of the
TransferText macro.