This seems to work with Powerpoint 2007.
As described in the comment, it takes a block of text (the TextRange), the starting position and length of file reference, also a LinkAddr. LinkAddr is essentially a DOS-style file reference, like "..\folder\ppfile.ppt".
The intention here is to launch another PowerPoint tool by invoking its show.ppt or show.ppsm file name. The file name can refer to some other directory using MSDOS file name stuff. I don't know whether it can span different machine platforms, but it seems to work within one Windows 10 system.
My difficulty in getting this to work was some full-path links to images, e.g. something like C:\blah\blah\image.jpg, in the Visual Basic code. PowerPoint didn't like these, instead asked about enabling macros, and just hung up when one of my file links were to be executed. By getting rid of the "macro" complaints, this suddenly started working.
Or maybe some bugs have been fixed in recent repairs to my 2007 PowerPoint tools??
Go figure...
Sub InsertLink(ByRef Trange As TextRange, fpos As Long, msglen As Long, LinkAddr As String)
' Insert an HTML link into the selected TextFrame.
' get the character range
Dim Hrange As TextRange
Set Hrange = Trange.Characters(Start:=fpos, length:=msglen)
' make it an HTML link
With Hrange.ActionSettings(ppMouseClick)
.Action = ppActionHyperlink
.Hyperlink.Address = LinkAddr
End With
End Sub
Presentations.Open? - BigBen