If Right(Attachment, 4) = ".TXT" Then
        Shell "NOTEPAD.EXE """ & Attachment & """", vbNormalFocus

That's how I make mine, this could also be helpful to you Double Double Quotes

Thank you Adam.  I am trying to reproduce Ricks work EXACTLY.  So to that end I need to know WHY mine doesnt work AND why I got the yellow highlighted error message.  What is the message telling me is wrong?   I need to fix it  before it allows me to continue.

Carol -

FYI - 99.9% of the time Richard provides a completed database that you can look at to learn by.
It's good that you are watching and building because it helps anchor it into the brain.

The database is useful to see where you made errors.  Sometimes you just can't see the forest for the trees.

The database can be found here:  Student Databases
I don't recall if it is password protected but if it is it is the same as for your course videos.

Access, by highlighting the line, is telling you "this is the line that has the problem". (Most of the time)

What is the error you are getting in the message box?  That will give you an indication of what is wrong on that yellow line.
For instance a syntax error means you don't have something typed correctly.  You might be missing a parentheses or quote or comma.

The text in the error matters when you are asking for help.  It helps us to guide you.

*****I have been stuck at this point for days and really want to learn what I am doing wrong.*****  Can someone please help???

@Adam
I used double quotes as suggested (see cut/paste below) and I still get an error (yellow highlighted text =  Shell "NOTEPAD.EXE """ & Attachment & """, vbNormalFocus"
__________________________________________
Private Sub Attachment_DblClick(Cancel As Integer)

If Right(Attachment, 4) = ".TXT" Then
    Shell "NOTEPAD.EXE """ & Attachment & """, vbNormalFocus
End If

End Sub
____________________________________________________

Access added a quote at the end of vbNormalFocus, (see below) but does not allow me to save.  If I remove the last quote, Access puts it back.

Shell "NOTEPAD.EXE """ & Attachment & """, vbNormalFocus"

@Scott:  Thank you for the link to Rick's database.  I have downloaded it and tried to determine what I am doing wrong.  Unfortunately I am still stuck.  

Carol,

You are missing a double quote.

Shell "NOTEPAD.EXE """ & Attachment & """", vbNormalFocus

Carol -
Here is a trick I use when trying to look at code.  The old eyes aren't as good as the once were.

Copy and paste the code into Notepad and zoom it in.

In this case I assume Rick's code is good and mine is not.
Paste your code on the next line and look for the difference.  It is a lot of times easier to see in larger type of something that is fixed width font.  

For instance trying to see the difference between " and ''.  The first is a double quote ( " ).
The second is two single quotes ( ' ' - space in between for clarity )

Now to understanding why.  Access is trying to help you out by putting in the extra quote at the end of vbNormalFocus.  It gets it correct most of the time but not always, as is demonstrated here.

This is something you just have to learn by doing over time.  The Double Double Quotes in syntax is probably one of the most difficult things to grasp.  Watch that video again and again until it clicks.

My opinion here so take this with a grain of salt:
You are also jumping in to the deep end it appears.  I see that you have started the Beginner Series but you obviously have the Open Other Programs Seminar which contains some more advanced topics.
You need to keep learning how to crawl before you can run.  Make sure you are building your knowledge base by going through the courses.  Don't get ahead of yourself.

BTW - I get it.  Sometimes you need to get something done and NEED to go a little out of your comfort zone.

@Scott and Alex

Thank you for your patience.  I have solved my issue.
I started over (yet again) and it seems to be working for me now.