what is the matlab code for template not found?

i am doing iris based project, in that i am using template matching technique to find location(x,y) of center of match region. But my code showing match to which ever image i give, i want it to find match for iris region only, if other images other than eye part, it should tell template not found, how to construct code please help me, here is my present code

htm=vision.TemplateMatcher; hmi = vision.MarkerInserter('Size', 10, ... 'Fill', true, 'FillColor', 'White', 'Opacity', 0.75); I = imread('board.tif');

% Input image I = I(1:200,1:200,:);

% Use grayscale data for the search Igray = rgb2gray(I);

% Use a second similar chip as the template D=imread('my.jpg');T=rgb2gray(D);

% Find the [x y] coordinates of the chip's center Loc=step(htm,Igray,T);

% Mark the location on the image using white disc J = step(hmi, I, Loc);

imshow(T); title('Template'); figure; imshow(J); title('Marked target');

[Image Analyst]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup