In your catalog you will see the workflow which is attached to catalog item:
You need to open that workflow and in that you need to add 'if' activity. ie.
You need to drag 'if' activity and drop where you want in your workflow. Also you need to add condition in that where you need to check variable is checked or not.
This 'if' activity will show you 'Yes' and 'No' options in workflow, you can redirect the flow according to your conditions.
I hope this will resolve your issue.
Thanks
Rajesh.
