namespace AdvertisingPublication.Utils
{
    public enum HTMLHelpCommand
    {
      HH_DISPLAY_TOPIC = 0,
      HH_DISPLAY_TOC = 1,
      HH_DISPLAY_INDEX = 2,
      HH_DISPLAY_SEARCH = 3
    }

    public class Utils
    {
        [DllImport("hhctrl.ocx", EntryPoint="HtmlHelp", CharSet=CharSet.Auto)]
        public static extern IntPtr HtmlHelp(IntPtr hWndCaller, string pszFile, int uCommand, int dwData);
    }
}
....
// Вызов конкретной страницы справки
IntPtr pHelp = Utils.Utils.HtmlHelp(
    (IntPtr)null, 
    "AdvertisingPublication.chm::/html/07_4_Simultaneous.html",
    (int)HTMLHelpCommand.HH_DISPLAY_TOC, 
    0);