Access report export to excel issue

Hello!
I got a problem when exporting a report from access to excel.
This report gets data from a very simple query (SELECT * FROM Table), and it got a very simple layout

- Page header:
Contains some static descriptions
- Details:
Some Textboxes on a single line bound to fields from the query.
Some other Textboxes showing the result of formulas.
- Page Footer:
Just a page number and a print date field.
- Report Footer
Some Textboxes showing the SUM() of the fields in the details section.

Now, surprise.
I can export to excel with DoCmd.OutputTo perfectly.

The second step involves the creation of formulas in the report footer section.
In details section I have fields like "=A/B".
In the footer I have fields like "=SUM(A)/SUM(B)".
When I preview the report I get both type of field working.
But in the EXCEL file I can't see the second type.
I tryed some solutions but I still can't see that kind of formula.

Thanx

-- EDIT WOOOOOOOOOOOOOPS !!!