This is so someone does not pull their hair out like I just did. I cannot find anywhere in the documentation where this is explained so here it is:
1. Create your custom table
2. Create the drilldown page with SourceTable to your custom table
3. Save the page and REMEMBER THE ID
4. Go to the table property on the table you created in step 1
5. TYPE IN the Page ID in the DrillDownFormID property in step 4
6. Save and test your work.
In the table designer, there’s no place to specify the Drilldown Page. So you will need to use the DrillDownFormID property on the table even though there’s no forms created.
<Posted edited, thanks to a3arn for confirm that you do not need to create a form>
If you look through the standard objects, you’ll notice that the drilldown FORMS have the same ID as the drilldown PAGES. Tricky….