Show All Comments for 10 Seconds

I want to show all comments on my spreadsheet for 10 seconds upon opening the workbook. Then I want all the comments to hide. I am not a programmer. I am using the following code under workbook and not in a separate module:

Option Explicit
Private Sub Workbook_Open()
Dim c As Comment
For Each c In ActiveSheet.Comments
  c.Visible = True
Next
Application.Wait Now + TimeValue("00:00:10")
For Each c In ActiveSheet.Comments
  c.Visible = False
Next
End Sub

Needless to say it doesn't work.

Can someone put me straight please. I am attaching my file with this post.

Thanks in advance.