If I understand what you asking correctly, you which you have a switch, supplied for an existing junction box, to go on and supply a second junction box which will have a number of lights connected to it.
There is no reason you can't do that, but bare in mind:
a) you need to bring the neutral from the first junction box, directly into the second, and the live needs to go via the switch.
b) all the lights connected into your second junction box will be operated by the new switch
c) the total current consumption of the new lights must not exceed that of the maximum current of the wiring used, or the junction boxes (this is unlikely anyway, but worth considering if you are adding a lot of lights, or a number of outdoor floodlights etc... and as you haven't stated any details, thought it best to mention!