matlab gui slider in for and while loop

• hi everyone, im working on the image processing GUI and i want to change a value by using slider but i didn't do it. is anyone help me?*

vid = videoinput('winvideo', 2, 'YUY2_640x480');
set(vid, 'FramesPerTrigger', Inf);
set(vid, 'ReturnedColorspace', 'rgb')
vid.FrameGrabInterval =5;
start(vid);
while(vid.FramesAcquired<=100)
if get(handles.pushbutton1,'UserData')==0, break; end

    img_orig = getsnapshot(vid);
...
...
...
for r=0:ax*0.85   //i want to change 0.85 constant with slider
     for th=0:0.1:360

         x=r*cos(th*d);
        y=r*sin(th*d);
        xx=fix((x)+bc(1));
        yy=fix((y)+bc(2));
end
end
...
...
..