How to make an external log using Excel VBA?

Question

The code has been updated to reference the changes below.

This log system create an external document for Excel called Log.txt, it will create a line in the log.txt

Answer 1

The problem is that when the you enter the merged cells, the value put into PreviousValue (in Worksheet_SelectionChange) is an array of all of the merged cells, which you can't compare to the the new value. When Worksheet_Change is fired on the edit, the target is only the top-left cell of the merged range. So let's just track that cell for merged ranges. Replace your Worksheet_SelectionChange with the following:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    PreviousValue = Target(1).Value
End Sub

Disclaimer: This was tested on Excel for Mac 2011 as I don't have access to Excel for Windows at the moment, but I'm pretty sure that it will work on Excel for Windows as well.