returning the number of rows output by a copy command from a function

I have a function that generates a table of records and then a SQL statement
that does a COPY into a text file. I want to return the number of records
output into the text file from my function. The number of rows in the table
is not necessarily the number of rows in the file due to summarization of
data in the table on the way out. Here is a very shortened version of what
I'm doing:

CREATE OR REPLACE FUNCTION export_data(list of parameters)
RETURNS integer AS
$BODY$

declare
My variables

Begin

{ A lot of SQL to build and populate the table of records to export}

strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with CSV
HEADER;';
Execute strSQL;

Return 0;

end
$BODY$
LANGUAGE plpgsql VOLATILE

strSQL gets dynamically generated so it's not a static statement.

This all works exactly as I want. But when I try to get the row count back
out I cannot get it. I've tried the following:

1.
strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with CSV
HEADER;';
Execute strSQL into export_count;

Return export_count;

This give me an error saying that I've tried to use the INTO statement with
a command that doesn't return data.

2.
strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with CSV
HEADER;';
Execute strSQL;

Get diagnostics export_count = row_count;

This always returns zero.

3.
strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with CSV
HEADER;';
Execute strSQL;

Return row_count;

This returns a null.

Any way to do this?

Thanks in advance,
James