The date_time in cell G3 should remain the same when you open the workbook saved using the macro and will only change if you run the macro again. It sounds like you are reopening the latest file (saved in your specified location) and running the macro from this file.
With, for example:
dailytaskpath = "C:\"
dailytaskfile = Format(Date, "ddmmyyyy") & "_" & Format(Time, "hhmmss")
How about something like this, using the workbook name to define the date and time stamp in cell A1 when the workbook is opened:
Private Sub Workbook_Open()
Dim date_time As String
Dim format_date_time As Date
date_time = Application.Substitute(ThisWorkbook.Name, ".xls", "")
format_date_time = Left(date_time, 2) & "/" & _
Mid(date_time, 3, 2) & "/" & Mid(date_time, 5, 4) & " " _
& Mid(date_time, 10, 2) & ":" & _
Mid(date_time, 12, 2) & ":" & Mid(date_time, 14, 2)
With Sheet1.Range("A1")
.Value = format_date_time
.NumberFormat = "dd/mm/yyyy hh:mm:ss"
End With
End Sub
Copy and paste the code into the ThisWorkBook module in the Visual Basic Editor.
Bookmarks