Dialog Workflow Multiple respondents/authorisers

Hi all,

I am trying to create a change request process with workflow.  I've set up a form start workflow dialog that allows a user to create a Change request and then submit it for authorisation.  

The dialog sends emails out to a group of authorisers with a respond link.  The first person that clicks the link can go though and progress the workflow but I was hoping to set it up that two people had to respond before it would go to the next stage.  Is there a way to do this?

Also when the second person responds it will redirect to an error page is there not a way of sending further respondants to a a custom error page for that dialog workflow component?