Unfortunately Outlook express does not have any calendar. You could use Mozilla Sunbird instead and even better you can attach Mozilla Sunbird to Mozilla's email program Thunderbird with Mozilla Lightening.

Sunbird can be used by itself or integrated with Thunderbird, so take your pick.

Here are the links:

http://www.mozilla.org/projects/calendar/
http://www.mozillamessaging.com/en-US/thunderbird/