Open Multiple Files Via GetOpenFileName

I'm having problems with the multiselect argument of the getopenfilename function. I've used this dozens of times with no problems, but now it doesn't work for me. I tried copying and pasting code that works in one module,

What I'm using is

Sub OpenFiles()
Dim vFiles As Variant, iNumfiles As Integer

vFiles = Application.GetOpenFilename(MultiSelect:=True)

If IsArray(vFiles) Then
For iNumfiles = LBound(vFiles) To UBound(vFiles)
MsgBox vFiles(iNumfiles)
Next iNumfiles
End If

End Sub

pretty simple, expect that when I select multiple files in the open dialog box, vfiles is a string containing one of the filenames, not an array containing them all! (by selecting, I simply highlight all the fiels I want and click open)