I believe that the File Dialog might be what you want. It only let's the user select a folder. You would then be free to name the files yourself.
Dim fb As New FolderBrowserDialog
fb.Description = "Select the Folder"
fb.RootFolder = Environment.SpecialFolder.MyComputer
Dim dlgResult As DialogResult = fb.ShowDialog()
If dlgResult = Windows.Forms.DialogResult.OK Then
savefolder = fb.SelectedPath
End If
There you go.