I suspect you want to do something like:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim i As Long, j As Long, StrTmp As String
With Selection
For i = 1 To .Cells.Count
StrTmp = .Cells(i).Value
For j = Len(StrTmp) - 1 To 1 Step -1
If Mid(StrTmp, j, 1) = Chr(10) Then
If (Mid(StrTmp, j - 1, 1) <> Chr(10)) And (Mid(StrTmp, j + 1, 1) <> Chr(10)) Then
StrTmp = Left(StrTmp, j - 1) & " " & Right(StrTmp, Len(StrTmp) - j)
ElseIf (Mid(StrTmp, j + 1, 1) = Chr(10)) And (Mid(StrTmp, j + 2, 1) = Chr(10)) Then
StrTmp = Left(StrTmp, j - 1) & Right(StrTmp, Len(StrTmp) - j)
End If
End If
Next
.Cells(i).Value = StrTmp
Next
End With
Application.ScreenUpdating = True
End Sub