Is this tool texture possible?

Say I have a closed-off room that it s not possible to get into. The only space linking this room to the map's playable space is a brush-based, func_detail window with frame that completely seals its hole; the player will never see the other side of this window or its frame.

At the moment, I add nodraw to the back of the window frame but leave the back of the window itself as the same glass texture as on the front, in order for light inside the room to be cast outside. Would it be possible, though texture flags, to create a tools texture that acts in exactly the same way as nodraw (ie it isn't rendered) but does not cast shadows? In this case I would be able to apply it to the back of my window, have the window not render its back face but still have light cast through it.

My problem comes in the situation I have now, where I have a grating around the bottom of generators (like in Turbine) and lights underneath that need to shine through. Because of the shape of the grating (there's a circle cut out of the middle), for each of the four generators there would be sixteen faces underneath that would need to be textured with the light-permitting grating texture, which is where my problem comes. I could just use a func_brush with no shadowing, but I'm sure there must be a more elegant solution than that.

Thanks, I'll check out blockbullets, then. Seems like this texture is useful for pretty much anything, the amount it seems to be solving my recent problems...