Preventing access/bypassing junction folders when calculating folder sizes in userprofile folders

I am attempting to write a program that displays the full folder sizes of a specific group of folders. Right now it's only set up for the userprofile "Documents" folder.

Here is my code:

Imports System
Imports System.IO

Public Class BackupperForm
    Dim TotalSize As Long = 0
    Public Function GetDirSize(RootFolder As String) As Long
        Dim FolderInfo = New IO.DirectoryInfo(RootFolder)
        For Each File In FolderInfo.GetFiles : TotalSize += File.Length
        Next
        For Each SubFolderInfo In FolderInfo.GetDirectories : GetDirSize(SubFolderInfo.FullName)
        Next
        Return TotalSize
    End Function

    Private Sub calButton_Click(sender As Object, e As EventArgs) Handles calButton.Click
        TotalSize = 0 'Reset the counter
        Dim TheSize As Long = GetDirSize(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile) & "\Documents\")
        MsgBox(FormatNumber(TheSize, 0) & " Bytes" & vbCr & _
               FormatNumber(TheSize / 1024, 1) & " Kilobytes" & vbCr & _
               FormatNumber(TheSize / 1024 / 1024, 1) & " Megabytes" & vbCr & _
               FormatNumber(TheSize / 1024 / 1024 / 1024, 1) & " Gigabytes")
    End Sub
End Class

Every time it runs, it obtains the correct directory but when it tries to access the junction folders (My Music, My Pictures, My Videos, etc.) under "Documents" I get an Unauthorized Access error, as I should. Junction folders are not accessible by design. However, I cannot figure out how to bypass those folders when trying to get the size so an exception doesn't get thrown.

Can anyone assist?