title: Extjs GridPanel selections from database
body: <p>My idea is to have a combobox filled with sectors, and a list of users below with checkboxes to indicate if each user belongs to the selected sector.</p>
  
  <p>The sectors are stored in my database and each user can have their id linked to one or more sectors.</p>
  
  <p>I know how to fill the combo with the sectors, and the grid with the users, but how can I make a checkbox for each user which changes depending on the sector selected?</p>
  
  <p>And then, could I update those selections to my database?</p>
  
  <p>I'd really appreciate any help.</p>