Adding/removing buttons at runtime

My aim is have my time clock app handle people who work in multiple departments. Currently, with single departments only, an employee either double-clicks his/her name in a LIST-PANEL or clicks on the name and then on a button (appropriately labeled “Clock Joe In” or “Clock Joe Out”) to clock in or out.

For the vast majority of employees, who are single-department, I want to keep it that simple. For multi-department employees the simplest thing I can think of is to replace the single CLOCK IN/OUT button with a button for each of the departments they could be clocking into.

I was hoping there would be a simpler way than this stripped-down code (on Mac OS, by the way):

(defparameter *in* t)

(defun click-clock-button (interface)
  (setf *in* (not *in*))
  (setf (capi:item-text (clock interface))
        (if *in* "You're in!" "You're out!"))
  (setf (capi:pane-layout interface)
        (make-instance 'capi:column-layout
                       :description
                       (append
                        (list (clock interface))
                        (when (not *in*)
                          (list
                           (make-instance 'capi:push-button :text "Grocery")
                           (make-instance 'capi:push-button :text "Produce")))))))

(capi:define-interface clock-interface ()
  ()
  (:panes
   (clock capi:push-button
          :accessor clock
          :text "Clock In/Out"
          :visible-min-width '(character 20)
          :selection-callback 'click-clock-button
          :callback-type :interface))
  (:layouts
   (main-layout capi:column-layout '(clock ) :gap 10 :adjust :center))
  (:default-initargs :title "Button Test"))

(capi:display (make-instance 'clock-interface))

I tried including a BUTTONS pane (whether a COLUMN-LAYOUT or PUSH-BUTTON-PANEL) in the CLOCK-INTERFACE and simply SETFing the ITEMS or DESCRIPTION of that pane. I can see from (BUTTONS interface) that it works, but then, even trying an assortment of SETFing, INVALIDATE-RECTing, etc., I couldn’t get the result to show up in the CLOCK-INTERFACE window.

So this simplified code succeeds, but the CLICK-CLOCK-BUTTON callback would have to include the entire PANE-LAYOUT for the window. The actual layout is not terribly complicated, but this seems like a clumsy solution.

ALTERNATIVES
I expect someone will offer a completely different approach, like opening a dialog window or having a pop-up menu to select the department, but I want to preserve two-click simplicity for the single-department people and not tax the dexterity of people who may be clumsy with computers. I’m open to alternative design ideas, but I’d still like to see a solution to the problem as I’m posing it.

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