Create following formula within the Section Expert.
Remainder((recordnumber),25) <> 0;
To apply this formula in the Section Expert:
1. Right-click on the details section and click ‘Section Expert’.
2. On the ‘Sections’ list, click the details section.
3. Leave the check box cleared and click the ‘X+2′ command button next to ‘Suppress (No Drill-Down)’.
The formula editor opens.
4. Type the formula provided by this article.
5. Save your formula and close the formula editor.
6. Click OK in the Section Expert.
You will now only see every 25th record. All other records do not display on the report because of the conditional suppression at the details level.