Rem Versuch macht klu.....
Sub TestThis()
Dim strLookAt As String
Dim rngUsed As Range, c As Range
Dim lngx As Long
Sheets.Add
Range("A1").Select
Range("A2").Value = "a a"
Range("B3").Value = "b b"
Range("C400").Value = Chr(32)
Range("DD500").Value = " "
MsgBox "UsedRange " & ActiveSheet.UsedRange.Address
strLookAt = " "
MsgBox "found at " & Cells.Find(What:=strLookAt, LookAt:=xlWhole).Address
MsgBox "found next " & Cells.FindPrevious.Address
Set rngUsed = ActiveSheet.UsedRange
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False
Set rngUsed = ActiveSheet.UsedRange.SpecialCells(xlCellTypeConstants, 23)
For Each c In rngUsed
c.Value = WorksheetFunction.Clean(c.Value)
c.Value = Trim(c.Value)
Next
Application.Calculation = xlCalculationAutomatic
Application.ScreenUpdating = True
MsgBox "UsedRange " & ActiveSheet.UsedRange.Address
If Not Cells.Find(What:=strLookAt, LookAt:=xlWhole) Is Nothing Then _
MsgBox "found !"
If Not Cells.FindPrevious Is Nothing Then _
MsgBox "found next !"
End Sub