Help Needed

Hi,
We are trying to develop a website( role based-content management system).
The requirements are as follows:

There will be a menu option ("Application Form")on the frontpage.
When the end-user clicks on Application Form menu,it should display a form with following text fields.
- Name of Applicant
- Department
- Address
- Email Address
-Submit button

when the user clicks on Submit button,the form should be forwarded to user with the login-ID "CLERK".
Now,the CLERK needs to approve the form submitted by END-USER ,after getting approval from CLERK,the form should be forwarded to SITE-ENGINEER.When the SITE-ENGINEER approves it,it should be forwarded to ENGINEER.

FYI,CLERK,SITE-ENGINEER and ENGINEER are the authorized users who will log-in using there IDs and will act as a authorised person to approve the request.

In short the flow should be like this............
Step I:End user will fill-up the Application Form and submit the form.
Step II:When CLERK will login,the submited application form will wait for approval from CLERK.
Step III:When SITE-ENGINEER will login,the clerk approved application form will wait for approval from SITE-ENGINEER.
Step IV:When ENGINEER will login,the site-engineer approved application form will wait for approval from ENGINEER.

I mean,there will be four users,ENDUSER,CLERK,,SITE-ENGINEER, and ENGINEER and ENDUSER doesn't require any login.The Application Form option will be available on the front-page.Any one can access and use the application form to submit his/her application but it is the resposiblity of CLERK,SITE-ENGINEER and ENGINEER to process that form and put proper comments on the request either on APPROVAL or REJECTIOn of application.

Please guide me to implement such application.Detail guidance is expected as it is URGENT.

I await your reply.