title: Initializing combo boxes in worksheet (not form) -- Error: object required
body: <p>I have two combo boxes in Sheet2 (not a UserForm), named Xchoose and Ychoose. I would like to populate them with values from cells in Sheet1 when the workbook is opened.</p>
  
  <p>At this point, I am unable to even add a static string to the combo boxes. Here is my setup so far...</p>
  
  <p>In ThisWorkbook, I have:</p>
  
  <pre><code>Sub Workbook_Open()
      Call Sheet2.Init_Lists
  End Sub
  </code></pre>
  
  <p>In Sheet2 (Compare), I have:</p>
  
  <pre><code>Sub Init_Lists()
      MsgBox "Initializing..."
      Xchoose.AddItem "item 1"
      ' This subroutine will eventually add values from Sheet1.
  End Sub
  
  Sub Xchoose_Change()
      ' To do.
  End Sub
  
  Sub Ychoose_Change()
      ' To do.
  End Sub
  </code></pre>
  
  <p>The "Initializing..." message box appears when the workbook is opened, indicating that <code>Init_Lists</code> works properly, but then the program breaks on the line</p>
  
  <pre><code>Xchoose.AddItem "item 1"
  </code></pre>
  
  <p>with the error "Object required." I have tried putting the subroutines in a separate module, but I receive the same error.</p>
  
  <p>Can somebody explain how I can add items to these combo boxes? Thank you!</p>