Option Explicit
Sub DateienLesen()
    Call EventsOff
    Dim DateiName As String
    DateiName = Dir("C:\Temp\" & "*.xls")
    Do While DateiName <> ""
        If ThisWorkbook.Name <> DateiName Then
            Workbooks.Open Filename:="C:\Temp\" & DateiName
            Workbooks(DateiName).Worksheets(1).Range("A3:E" & Workbooks(DateiName).Worksheets(1).Range("A" & Rows.Count).End(xlUp).Row).Copy _
                ThisWorkbook.Worksheets(1).Range("A" & ThisWorkbook.Worksheets(1).Range("A" & Rows.Count).End(xlUp).Row + 1)
            Workbooks(DateiName).Close SaveChanges:=True
        End If
        DateiName = Dir
    Loop
    Call EventsOn
End Sub  

Public Sub EventsOff()
    With Application
        .ScreenUpdating = False
        .EnableEvents = False
        .Calculation = xlCalculationManual
    End With
End Sub  

Public Sub EventsOn()
    With Application
        .ScreenUpdating = True
        .EnableEvents = True
        .Calculation = xlCalculationAutomatic
    End With
End Sub