Hi again - I have the following model: (defmodel workarea (ctk::widget ctk::window) ((visiblep :accessor visiblep :initform (c- in :undefined) :initarg :visiblep)) (:default-initargs :id (gensym "WORKAREA-"))) This workarea is meant to work as a manager for kids that will be displayed if visiblep (yeah, it's not visible-p ;-) is t and will be invisible when visiblep is nil. Question now is how that can be done... Via an observer that walks all kids and configures them as invisible? If so, then I have the following questions: 1. Tk-related: How to configure arbitrary objects as invisible ? 2. Cells-related: How to walk a family object's kids to call a function with the paths of the kids ? Thx! Frank