I don't think Microsoft has documented how you can develop software to change an Outlook password. Furthermore, I don't think Microsoft has documented Outlook Profile registry format well enough that I would want to try and develop software to alter it.
Here are some other options that may or may not work for you:
1. You can setup multiple Outlook Profiles (a profile is one or more email accounts) using Control Panel / Mail. Then you can select which Outlook Profile is the default or whether Outlook should prompt for which Outlook Profile to use. I used this several years ago and haven't done it on my current Outlook installation. I remember that there is a way to pass the Outlook Profile name as a command line parameter so you could have a separate shortcut for each profile.
2. Use an Outlook Profile (*.PRF) file to create an Outlook Profile. The Microsoft TechNet web site has an article titled
Customize Outlook profiles by using an Outlook Profile (PRF) file[
^]. It looks like you have to download the
Office Customization Tool[
^] from Microsoft's web site. I have never used this.