I've got a situation in which I need to use a J-box to extend an existing run. Unfortunately, the box will be placed in a location where, for aesthetic reasons, I'd prefer not to install an access panel. I thought I could install a light to circumvent this problem, but the boxes that come with small recessed halogen fixtures (my preference in this case) are too small to accommodate 3 12/2 conductors (power in, 1 beginning of the run switch, power out). Would it be code to install a j-box on the joist next to fixture such that access to the box is via the fixture hole in the drywall ceiling?

Thanks!

-TRS