The last time I did this, I had a Word document with named bookmarks. Each form had a HELP button that supplied a form code. I had a table of help topics that were valid for various form codes. Net result was that I popped up a drop-down (Listbox) that was single-select. Each title in the help list had 3 parts but only the topic name was visible The other parts were the code from the button and the name of the bookmark in the word document.
If you clicked for Help and selected a topic, I would take the bookmark text, open a Word Application, from there open the Word help document Read-Only, bring it to top, and cause it to go to the specific bookmark. The user would also get an instruction to close Word when done.
If you have a reasonably literate user base that knows left from right then you have a good chance that what I described would work.