impoint and updating the coordinates

I've created a gui, and there's a part where the user should be able to choose 2 pixel on the loaded image and then the program runs another function with the coordinates of those 2 pixels. I did it with ginput but now now I want to do it with impoint and I want also that the program updates the coordinates when the user changes those points. I just started to use Matlab, I would really appreciate if someone helps me.

x,y] = ginput(2) 
handles.X = x; 
handles.Y = y; 
guidata(handles.PixelSelectionButt,handles) 
[Xpath Ypath] = catetherPathFast((1-VessN).*im2double(I),y,x); axes(handles.ShowImage); 
hold on 
plot(Ypath,Xpath,'b-'); 
hold off