Email Using VBA., Part III: Getting attached

In the first two parts of this series the problem of the disappearing signature and the ugly fonts were addressed.  Part III involves adding an attachment, when needed.

Since I was writing a subroutine to be used like a utility, the content parameters were optional.  That way, I could call the subroutine with a distribution list or without, with or without someone for the CC list, with or without Subject or a message for the body.  All worked fine with optional parameters.  As a reminder, there is the code so far:
    With EmailItem     
        .Display         
        .To = Recipients
        .CC = CopiesTo
        .Subject = Subj
    End With

This called for another optional parameter, AttachmentLocation and this to the With EmailItem block
          .Attachments.Add AttachmentLocation     

It worked properly if there was a valid string passed through AttachmentLocation but error-ed when AttachmentLocation was not available. In this case the action needed to be executed after the With EmailItem block, with a controlling If.
    If (AttachmentLocation) Then
        ChDir (PathFromFullFileName(AttachmentLocation))
        EmailItem.Attachments.Add AttachmentLocation
    End If

The IsAvailableFile is a function that tests AttachmentLocation.  IsAvailableFile checks character strings to see if they point to actual files.  (See Is it there?)