To enable remote SQL connections with SQL Server Express please use the following steps:

Click Start => Programs => Microsoft SQL Server 2005/2008 => SQL Server Configuration Manager.

Select SQL Server Network Configuration

Double click on Protocols for SQLEXPRESS

Right click TCP/IP and select Properties

Click on the IP Address tab, and then under IP2 IP Address, enter your IP Address

Scroll down to IPAll make sure TCP Dynamic Ports is blank and that TCP Port is set to your custom port

Click OK

Make sure that your custom port is enabled on your firewall and that mixed mode authentication is enabled for remote connections

When using SQL Express you will also need to open UDP port 1434

You may also find the following documentation helpful:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;91427