change the agent dynamically

Hi I am new to this Work flow and wanted to know it conceptually.

I have a adobe form and when the submit button is pressed it should go to his approvers box. how do we do this.

Submit button pressed ->control goes to backend class ->determine the new agent(approver ).. upto here no issues..

how do we pass the new agent (approver ) to the workflow so that the item goes to his box..

any help would be appreciated .. Thanks!