Combine the inputs together such that each series is a column, then use the option 'stack'
:
A = [495 500 500 195 210 100 70 65 85 265 320 430]';
B = [193 193 193 193 20 193 193 193 193 193 193 193]';
bar([B,A],'stacked')
EDIT addressing comment:
% Create random data and filler
A = randi(100,10,1);
B = randi(100,10,1);
mxA = max(A);
filler = mxA-A;
% Plot stacked bar chart
h = bar([A,filler,B],'stacked');
% Set the filler to transparent
set(h(2),'Face','none','Edge','none')
% Set y-labels
yticks = linspace(0,max(B),5) + mxA;
set(gca,'Ytick', [linspace(0,mxA,5) yticks(2:end)],'YtickL', [linspace(0,mxA,5) yticks(2:end)-mxA])