'...
Private Thread_AD_Query As Threading.Thread = New Threading.Thread(AddressOf _
  GetRealName)
'...
Private Sub OpenFileDialog_FileOk(ByVal sender As System.Object, ByVal e As _
  System.ComponentModel.CancelEventArgs) Handles OpenFileDialog.FileOk
        '...
        Thread_AD_Query.Start()
End Sub
 
 Sub GetRealName()
        Dim b1 As Boolean = False
        Dim b2 As Boolean = False
        Using Searcher As New DirectorySearcher(New DirectoryEntry)
            Searcher.Filter = "(&(sAMAccountType=805306368)(objectClass=user)(!(" & _
              "userAccountControl:1.2.840.113556.1.4.803:=2)))"
            Searcher.PropertiesToLoad.Add("Name")
            Searcher.PropertiesToLoad.Add("DisplayName")
            Dim UserAccount As SearchResultCollection = Searcher.FindAll
            For Each a In UserAccount
                If a.properties("Name")(0) = TxtKlassifizierer.Text.Replace( _
                  "Domain\", "") Then
                    'Hier knallt es immer
                    LblKlassifiziererRealName.Text = a.properties( _
                      "Displayname")(0)
                    b1 = True
                End If
                If a.properties("Name")(0) = TxtAutor.Text.Replace("Domain\", _
                  "") Then
                    'Hier knallt es immer
                    LblErstellerRealName. vText = a.properties("Displayname")(0)
                    b2 = True
                End If
                If b1 = True And b2 = True Then
                    Exit For
                End If
            Next
        End Using
    End Sub