You can use the param parameter to provide further refinement of the Topic, TopicId, KeywordIndex, or AssociateIndex command. If the value specified in the command parameter is TableOfContents, Index, or Find, this value should be an empty string. If the command parameter references Topic, TopicId, KeywordIndex, or AssociateIndex, this value should be a string that contains the topic name, or the keyword or numeric identifier of the topic to display.
So answer was to do:
Help.ShowHelp(ParentForm, "helpFile.chm", "topicURL.htm")
The topicURL Found right clicking on opened topic:
then copy url: