Its ok if you can't upload, I am starting to get what you are looking for.
For that, you will have to do a little more work. This is what I would do for this.
Add 2 new Fields, named Column1Selected and Column2Selected (Name as you wish), set as boolean, set to false.
Now for every Checkbox in Column1, add a rule to check if Column1Selected is set to false and if this Checkbox is checked, Add Action to set Column1Selected to true.
Also add a rule to check if Column1Selected is set to true and if this Checkbox is checked, Add action to popup message.
Do the same for Column2Selected. It is more work.
When I said to make sure they are in order, if the are put in, in the wrong order, the rules won't work correctly. (A comes before B kind of thing)
You can probably ignore the previous post since I was still confused on what you needed.