Re: [2005] Form Status...
That's what data binding is for. You might have your Departments in a List(Of Department). You bind that List to your ComboBox. When you open the Departments dialogue and add a new Department you add it to that same List. You then call ResetBindings on the BindingSource and it will refresh the items displayed in the ComboBox from the List. It's this sort of thing that makes data-binding incredibly useful, despite some people's determination that it is inherently wrong (not you, someone else).
Re: [2005] Form Status...
You can transer data between two forms by creating some properties on your first form so the second form can read and set it as needed. Then in your first form, when the second closes from being displayed with .ShowDialog, you can refresh the dataset that should be bound to your combo and read the forms property to see what was set from the popup form.