imcrop interactive image with coordonates

Hey guys! I need a gui interface that load images from a folder and then crop the photo interactive. I managed to do the loading with a push button and now i created 4 edit text in order to the user to initialize the 4 coordonates for cropping; xmin,ymin,width,height. the problem is that now i need to do a check box that calls the 4 previews parameters and the image that has been loaded and crop the image with those characteristics. I hope you can help me. Thank you!