Frame range node for compositor

There are occasionally situations where you might only need separate passes for particular frames and not the entire animation, so I think it would be handy to have a frame range node that can sit between the compositor and the output node. In this, you could specify a start and end point. This should be stackable, so for example if you want to render the gloss reflection pass from frames 40-120 as well as from frames 220-290, you can use two nodes. Alternatively, you could have one node to rule them all in which you can type a range and/or frame list, ie. 1-50, 75, 85,95-100 You can specify frames like this in other software such as 3DS Max. But as Blender works on start and end point only, perhaps the first kind of node would be easier to create.