It's been a long time since I used Crystal 7. Do you have the option to create a Running Total? If so, here's what you do:
Create a running total that will count your records. I'll call it {#RecordCount}. Open the Section Expert. On the details section (or whereever you need to have the page break) click on the formula button next to "New Page After" and add the following formula:
{#RecordCount} mod 40 = 0
This will tell Crystal to create a new page if there is no remainder when the record count is divided by 40 (meaning 40 records have been printed on this page.)
You may have to play with whether there is a check-mark in the box after "New Page After" to get this to work right.
-Dell