How to limit kriging plot to a certain kriging variance?

Dear all, I would like to limit the plot of my kriging results to a certain kriging variance, saying 0.19. I'm using the variogram modelling and ordinary kriging scripts by Wolfgang Schwanghart. Currently, the code allows to limit to a certain range (I = D<100), but how can I change it to something like "zivar should be maximum 0.19"?

    % dx = 10;
xi = min(x2016):dx:(max(x2016)+dx);
yi = min(y2016):dx:(max(y2016)+dx);
[xi,yi] = meshgrid(xi,yi);
[IX,D] = knnsearch([x2016,y2016],[xi(:) yi(:)],'k',1);
I = D<100;
[zi,zivar] = krigingknn(S2016filt,x2016,y2016,twt2016filt,xi,yi);
zi(~I) = nan;
pcolor(xi,yi,zi)