I gather the submit button isn't actually a 'send via email' button because then the user wouldn't accomplish anything by going back and changing fields, because it is already sent!
Maybe a 'preview' button is what you mean - which you can do by designing a view a bit like a 'print view' which consists of all the fields they need to see on one page in a more 'report' like fashion (just using formatting on the controls, and lock them) - switch to this view when the 'preview' button is pressed, and put your real submit button on this page.
When they push the real submit button, set a hidden field value to something which can tell the form it is at the 'approval' phase - I use 'formMode' and give it a number which indicates where in the 'approval' chain the form is.
Then use Form Open rules to check the value of this field, and switch to a different view -
For your 'supervisor' view, unless they need to change any of the fields, just give them the same 'preview' view you gave the user - except this time make the submit button go to the helpdesk. And if they have limited fields to fill in, put them in a section which is only visible when formMode = 1.
You could even use the exact same view without having to clone it, and put two conditional rules on the submit button, one for when formMode = 0 -> submit to supervisor and one where formMode = 1 -> submit to helpdesk.
Hope this one idea helps you on your way.