Excel other number

MargotKloeck 

You cannot do this with a formula, for a formula cannot refer to the cell itself. You need VBA code in the worksheet module:

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim rng As Range
    If Not Intersect(Range("E2:E1000"), Target) Is Nothing Then
        Application.ScreenUpdating = False
        Application.EnableEvents = False
        For Each rng In Intersect(Range("E2:E1000"), Target)
            Select Case rng.Value
                Case 40
                    rng.Value = 24.84 ' VBA uses decimal point, not comma
                Case 401
                    rng.Value = 27.32
                Case 25
                    rng.Value = 31.15
                ' add other cases as needed
            End Select
        Next rng
        Application.EnableEvents = True
        Application.ScreenUpdating = True
    End If
End Sub

See the attached version of your workbook. It is now a macro-enabled workbook, so you will have to allow macros. Right-click the sheet tab and select 'View Code' from the context menu to inspect and edit the code.