The IResponse::put_Expires method sets the current value of the Expires property of the Response object.
HRESULT put_Expires(
LONG lExpiresMinutes // LONG that contains the new Expires value
);
If the user returns to the same page before it expires, the cached version is displayed. If this method is set more than once on a page, the shortest time is used.
Response Object, IResponse::get_Expires