I am trying to do a visual object that will be a generic mult-stage button:

The "button" is in fact an image that changes when mouse goes over it and when the user click on it.
So I do a this.picture = image_?.jpg in mousedown, mouseup, mouseleave and mousenenter events.
It works find but I don't want the program to get the image on disk. I want it in memory like it does for the disablepicture property of a button. These pictures are automatically added to the project when you use them. Can we do the same ? Can we add a property to an object to keep these picture and that will add automatically the image to the project ?

Thanks for any help
Eric