You might require several subdomain for a specific domain, so you can add them virtually using following technique.
You need to add an A record in your dns setting using your hosting control panel, pointing to the IP of your domain
Now this will always redirect subdomain.hellowahab.com to you root page i.e
Now you can add following lines to your code (Code is C# specific you can change as per your language requirement)
case “http:// subdomain.hellowahab.com/”: