Start loop - end loop

Friends, please explain the logic of this function, make a simple touch button in which I need one function - search for an image on the page, in the case of finding a picture left mouse click, in the absence of a picture scrolling page at once, and all this needs to be looped, many times (about 500 or more)
When I try to use start loop and end loop - works only once, without options. What do I do differently than I do with these functions to make a normal multiple cycle?