// Determine the part the property sheet page is in
final IWorkbenchPart part = tabbedPropertySheetPage.getSite().getWorkbenchWindow().getPartService().getActivePart();
// If the part is a diagram editor, get the project from the diagram
if (part instanceof DiagramEditor) {
final DiagramEditor editor = (DiagramEditor) part;
final IProject project = ActivitiUiUtil.getProjectFromDiagram(editor.getDiagramTypeProvider().getDiagram());
// Determine the custom service tasks using the project found
return getCustomServiceTasks(project);
}