how to do image segmentation using edge detection?

hi, i have a square in an image where i want to segment it out for further processing. can someone tell me how can it be done? i have tried bounding box method but it end up detecting all the small title square at the background and i cant crop the square object that i want. thank you for your reply

[Image Analyst]

How effectively do you think we can do this without your image? Please upload it and tell us where you uploaded it to. (Try http://snag.gy)