I am trying to set-up a connection with a cable modem running to an ethernet switch. A desktop and the airport express are attached to the switch. The airport express is for the macbook (with an airport card). I cannot get both computers to connect to the internet at the same time. I have successfully connected to the internet on the imac and can see the airport express on the macbook (with a strong signal). However, the web browser will not connect to the internet on the macbook. I have also been able to get the macbook on the internet, but then the imac cannot connect. Is there a setting on the airport admin that I should have set, so that this can be done? The apple salesman at Best Buy told me to use this configuration with the express.

For hardware, I am using the D-Link DCM-202 modem and the D-link DES-1105 switch.

Is this possible, and if not what hardware would I need to have the imac connected with an ethernet cable and then also have a wireless router?