Xor thank's for the hint, got it now. The cells are not truely empty and there is no way to do this by a formular.

You can do it by VBA however:

Sub Empty_Cells()
Dim SomeRange As Range
Set SomeRange = Range("D29") 'COMMENT this means D2 : D9 without spaces, forum makes the smiley xD
For Each Cell In SomeRange
If (Cell.Value = "") Then Cell.ClearContents
Next
End Sub