Hi Goldy -
There are a few different ways to do this.
I think at it's most basic, you can setup a campaign like this, that says, smart list --> these people, flow...
Send email 1, wait a week, If they didn't open Email 1, then send Email 2.
However, it gets more complicated, because 1 week later, if they never were sent email 2, then technically they never opened it a week later.
So instead you'd need to create a master campaign, that adds people into this series of emails, and then campaign 2 is "Not was Opened Email 1" blah blah blah, Request Campaign 3. Then Campaign 3 is "Was sent email 2, Not Opened Email 2". Then send email 3.
It can be done as you describe it to be, but I wonder whether this is worth your effort. Would it not be easier to merely create an engagement campaign? Create 5 pieces of excellent content that everyone would want to enjoy, and not make your life complicated with campaigns and request campaigns.