Option Explicit
Public Sub logFile(ByVal Action As String, Optional Sheet As String, Optional ByVal Target As String, Optional ByVal Value As String)
Dim strLogFile As String, strTmp As String, strOld As String
Dim strAction As String * 15
Dim strSh As String * 12
Dim strAddr As String * 12
Const strSep As String = ", "
strLogFile = ThisWorkbook.Path & Application.PathSeparator & ThisWorkbook.Name & "_log.txt"
strTmp = Format(Now, "dd.MM.yyyy hh:mm:ss")
strTmp = strTmp & strSep
strAction = Action
strTmp = strTmp & strAction & strSep
If Len(Sheet) Then strSh = Sheet: strTmp = strTmp & strSh & strSep
If Len(Target) Then strAddr = Target: strTmp = strTmp & strAddr & strSep
If Len(Value) Then strTmp = strTmp & Left(Value, 1024)
If Right(strTmp, Len(strSep)) = strSep Then strTmp = Left(strTmp, Len(strTmp) - Len(strSep))
Open strLogFile For Binary As #1
strOld = Space$(LOF(1))
Get #1, , strOld
Close #1
strTmp = strTmp & vbCrLf & strOld
Open strLogFile For Output As #1
Print #1, strTmp
Close #1
End Sub