I am using HTML Help to display help information within my Excel program.
After I close HTML Help, the file system thinks that the .chm file is still
being accessed, and I cannot overwrite the file (although the HTML Help
process is closed). Here is the code that I have to open:

Call HtmlHelp(0, ActiveWorkbook.Path & "\MyHelp.chm", HH_DISPLAY_TOPIC, 0)
or
Call HtmlHelp(0, ActiveWorkbook.Path & "\MyHelp.chm", HH_HELP_CONTEXT, 1001)

and to close:

Call HtmlHelp(0, 0, HH_CLOSE_ALL, 0)