creating a dragable box

Hello, i'm trying to create a drag able box in one image, and use the [xmin ymin width height] of the box that i created as the new image.

i have the following code.

imshow(image_one)
rect = getPosition(rectHandle); 
         y=rect(1);
         x=rect(2);
         ny=rect(3);
         nx=rect(4);

i want to make the y,x,ny,nx my new image for image one.

the whole purpose of this is because i'm trying to isolate a certain part of the image. and compare it using mean square error to compute the difference.

p.s i would like to do the same to image_two aswell because to compute the MSE, the two variables have to have the same dimensions. (it needs to be a drag-able box. because the area i'm isolating in image_two is in a different area of the image in comparison to image one. so i was thinking maybe i could drag the box over the area of interest)

[Akira Agata]

How about trying an imrect function?

[KSSV]

How about imcrop ?