Get selection from other widgets in page

I’m trying to do something like described in the following topic:

I have a document with two table widgets, and would like to combine selected rows from both table widgets to create a button to add a row in a third table:

  • People
  • Projects
  • Button to add to add the selected Person and Project to the “Hours” table:
  • Hours with “People.ID”, “Projects.ID”, “Hours”