Within sphere collider to click on door that opens

Hi, I am trying to make a sphere collider that gives me the option to open a door when inside the sphere collider. The idea is that I am going to be able to click on the door in order to open it when I am inside the sphere collider, I already know how to make so that when I click on the object I trigger an event/animation. But all I want is that I can do that within a sphere collider and that I can't open the door from any other place than inside the sphere collider. Please help!