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

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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?