The PSM_QUERYSIBLINGS message is sent to a property sheet, which then forwards the PSM_QUERYSIBLINGS message to each of its pages. If a page returns a nonzero value, the property sheet does not send the message to subsequent pages. You can send the PSM_QUERYSIBLINGS message explicitly or by using the PropSheet_QuerySiblings macro.
PSM_QUERYSIBLINGS wParam = (WPARAM) param1; lParam = (LPARAM) param2;
Returns the nonzero value from a page in the property sheet, or zero if no page returns a nonzero value.