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