In the section expert, it is possible to supress any section including the detail section based on a formula that returns a boolean.
CLick on the x+2 button next to the suppress checkbox.
This button will turn red when there is a formula behind it.
The formula overides the check box, so unchecking the checkbox will not keep the formula from suppressing records.
It should also be possible to use the Show formula option in the select expert. That will not hide the records, but instead never return the records to Crystal.