line formation and angle measurement using gui in matlab?

Dear sir,

I need your help for the following

1. I need to select the region of an image by mouse
2. then i need to select(define) two points in the image
3. then i need to join these two points to draw a line
4. repeat step 2 and 3
5. now i need to find and display the angle between the lines drawn in steps 3 and 4.

If you send the code for above item , it ll be huge useful for me sir.

Thanks alot in advance..

[Sven]

Sounds fun, show us what you've done so far.