Create a Custom Login Page

Question

Hi, 

I'm developing a multiple-city Visitor's system. I want to create a Login page with following details:

Username, Password, City & Gate_Name.

I need to know how should I proceed with creation of tables and then the code.

The City & Gate_Name should be nested. When a city is selected, then only the appropriate gate-name must be displayed in drop-down box below.

Initially, Username & Password must be checked.

If they do not match, an error message must be generated. 

If they match, then the associated city & gate-name must be checked.

If they do not match, an error message must be generated. 

If all the details match, then a Session by UserID must be created and the user must be redirected to the Home Page.

A user allotted a particular gate cannot Login from any other city or any other gate.

Please help me with this Login Issue.

Thanks.