Windows API to Determine if File is Local/Convert Path to Drive Letter

[Johnny]

Hi all,

I'm working on a userform in Excel that relies on the common file
dialog windows api. Once the user selects a file, I need to determine
if the selection is valid or not. Basically, I need two additional
Windows APIs: one to determine if the file the user selected is stored
on the local machine or on a network share, and another to convert the
fully qualified name (\\server\folder) to the drive letter alias set up
on the local machine (i.e. o:\ in this case). Has anyone used APIs
like this/have a link to a site that would have these APIs documented?
(I rarely use Windows APIs, so I need the VBA implementation of them if
possible.)

Thanks,
Johnny