The experiment you ask for perhaps can be done in vnmrj, but would even so be tricky. Note that it does help (necessarily) to have a resolved carbon. Which proton(s) is(are) coupled to the carbon is what counts. One would have to decouple all the other protons except that(those) coupling to that carbon. The reverse experiment would be more straightforward, decoupling selectively. Here you would put a low power cw pulse on the proton you believe is coupling to the carbon of interest and it will remove that coupling selectively. Compare that to a fully coupled carbon and you should have what you want. Another alternative would be to run a coupled HSQC, which works fine for getting 1-bond C-H couplings. For long-range couplings, sequences such as HETLOC are useful. As usual with NMR, many variation exist depending on the specific compound and information needed.