I am looking for a solution to put a validation on required fields

I have a workflow in which if Manager approves the request no comments are required. If a request is rejected a comment field must be completed. I am able to validate when requestor is submitting a form (So initial form validation is not a problem). I want to validate as the workflow progress (I need help on this). 

For achieving this I am putting validation rule on when update button is clicked on approval state of the form because I want validation as the workflow progress (not the base state) please see the attachment.

In current scenario, with this rule when manager selects 'No' and try to submit it without comments it shows validation message but it also shows form has been submitted tab and upadate the sharepoint list with data. So rules are executing this way:
1. if current Workflow Activity is Manager Approval
2. and on view, Control contains 'No'
3. and the Form passes validation Configured
4. then complete the following one after another
 then on URLChangeControlForm SmartObject, execute its Update List Item method
 then hide URLChangeControlForm tab
 then show Submitted tab

 Rule 4. is inherited from the base state in approval state of the form (see attachment). In ideal scenario, it should only show validation message but should not show form has been submitted tab and upadate the sharepoint list with data.

Looking help on it. How can I fix this problem?