ReportBuilder has an open architecture for replacing any of the built-in dialogs. You can replace any of the built-in dialogs by creating a new form that inherits from an abstract ancestor and then registering it as the new built-in dialog.
For example, to replace ReportBuilder's print dialog you could:
The default dialog resides in RBuilder\Source\ppPDlg.pas and the form is called ppPrintDialog. You should assign your form a unique name, for example, myPrintDlg, and save the unit to another name. Also save the unit to the directory where your other forms are stored (not RBuilder\Source).
You will notice that the print dialog inherits from an ancestor TppCustomPrintDialog - this ancestor resides in ppForms.pas (where all the abstract ancestor forms for ReportBuilder are defined).
Declare an initializtion section at the bottom of the unit:
initialization ppRegisterForm(TppCustomPrintDialog, TMyPrintDialog);
Now your preview dialog should be automatically created and destroyed by ReportBuilder. The two page preview dialog in the RBuilder\Demos\Reports\Demo.dpro was created this same way. The only difference is the ppRegisterForm call is in then OnClick event of the button.