Determining if ToggleDockedState will toggle

I want to add a button that will toggle the docked state on a pane from floating to docked, and vice versa.  This button needs to be disabled if the ToggleDockedState can’t toggle the docked state.  An example of this would be a new window that starts out floating and does not have a previous dock location.  In this case, ToggleDockedState does not do anything. Conversely, if the new window is part of a layout, it has this information so ToggledDockState will toggle.  How can I determine if ToggleDockedState can actually toggle.  I’ve looked at numerous properties in the dock manager, but I cannot find the one that will tell me this.