how to make mouseover trigger something?

now ive tried the entire day to get this working, and nothing works… ive tried onmouseenter, onmousestay, ive tried raycast, ive tried ontriggerenter2D… nothing works…
What i need is, i have this shop, and i need to only be accessible when the mouse is over it, ie only register mouseclick when the mouse is hovering over the item. How do i go about that? I have a mouseenter function and a spriterenderer with a 2d collider attached, but when i right click, nothing happens! very frustrating, please help me

http://docs.unity3d.com/ScriptReference/MonoBehaviour.OnMouseOver.html