followhyperlink - hyperlink harmful message - RE 490: Cannot open.

[MetairieTom]

I have a list box based on the value list of a subdirectory of a directory on
a network drive. I seek to open the file (pdf, doc, xls) with
followhyperlink but keep getting the Runtime Error no matter what the method.
My preference is to build a string from a) the network drive and directory;
b) [ExamNo] the subdirectory where the files listed in the list box are; c)
the object file to be opened. I keep getting the RE 490: Cannot open the
specified file even when the system recognizes the file and displays the
harmful message dialog. Any help would be appreciated. Here is the code I
use in the double-click event of the listbox displaying the files:

Dim docstring As String
Dim ExamNo As String
Dim xdoc As String

ExamNo = Me.ExamNo.Value
xdoc = Me.DocList.Value
docstring = "R:\0ExamDocs\" & ExamNo & xdoc

FollowHyperlink (docstring)