The HtmlHelp API is simple in extreme; only one function (creatively called HtmlHelp).
I suspect the interface for the function API is not included in CVF module files (I have not checked, I just don't remember seen it in the past), so you might have to create the interface yourself.
To make it easier to use, most likely you'll need to translate into Fortran the structures used by the API, this should be straight forward, all the structures are described in the link John sent you before.
The only thing that might be confusing is the last argument (dwData). Depending on the content of argument uCommand, dwData is interpreted as a pointer or as a value, so you need to be careful here.
One more thing, remember that all the strings must be null terminated (i.e. C style).
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