waitbar2a(x, whichbar, varargin)

Progress bar (waitbar) that can be embedded into a GUI uipanel element and/or decremented.

The standard WAITBAR function (and the improved WAITBAR2 function, which this code is based on) must appear in their own figure windows, and cannot be embedded into a GUI.
WAITBAR2A is a drop-in replacement for either of the earlier functions, that has the additional capability to be initialized with the handle of a uipanel, in which case it draws into that uipanel rather than a new figure, and to be decremented.