Payment page after registerpage - final phase of project

hi ,
Am in final phase of my project , i have customized AD-Novus theme completely into a different look in my project which is for students to register and make payment to view particular page called test page , now @ final stage of this project i need to place a simple payment page after the register page ...its been a day i tried out this but its all ends in vain .i tried drupal_goto( ) at user_module_invoke() but this takes the user to corresponding page but without creating the account ??? Any help is really welcomed which helps me to finish the project..

Thank you ...