Hwo to write module for new CCK field

Hello,.. I'm totally new for Drupal Module Development.
I use Drupal 6.2. I need to create a module which will add a new field type to CCK. For example: My new type should contain Start Time, End Time, Description fields. But I need it not like a node, but like a field (widget?).
Could you please point my to the examples or description of how to do this. I couldn't find anything which I can use as a starting point.

Thanks a lot
Eugene