function g_UndoButtonCallback(varargin)
    % Whenever the user clicks on the 'Undo' button.
    
         global params oldparams paramEnabled oldparamEnabled selBlocks
    
         temp = paramEnabled;
         paramEnabled = oldparamEnabled;
         oldparamEnabled = temp;

         paramcommand = g_BuildParamCommand(params);
         for kk=1:length(selBlocks)
            set_param(selBlocks(kk),'Description',paramcommand);
         end
         g_AnnotationUpdate(params);
         
       % This to swap params and params, so it's possible to undo the undo:
         temp = params;
         params = oldparams;
         oldparams = temp;
         clear temp;

         ltpdagui('Redraw',2)
         
    end