Well the thing is, I often have objects which are getting light from another source which I want, but which overlaps. Then maybe I want the offending light to light up the area around the object, but not add to object. Making lights which don't make it to the object would also make them not go past the object. so limiting the range doesn't work in that case. Although it does work in other cases.

In other words, I have a table which is getting lit from a spot on a corner of a room. Now I have a rim light which has shadows turned off and does a nice job at backlighting objects and the floor, but it's too much when it hits the table. Turning the table's diffuse down is no good, and moving the spot is no good either, and I don't want to lose the rim light effect on the other objects - I just don't want it affecting the damn table.

So it would be highly useful to have an option for a light to be able to exclude having any effect on selected objects.

Thanks for the replies though, I might try to take some time to look into the whole python thing. :-)