  We study the possibility of measuring neutrino Yukawa couplings in the
Next-to-Minimal Supersymmetric Standard Model with right-handed neutrinos
(NMSSMr) when the lightest right-handed sneutrino is the Dark Matter (DM)
candidate, by exploiting a `dijet + dilepton + Missing Transverse Energy'
signature. We show that, contrary to the miminal realisation of Supersymmetry
(SUSY), the MSSM, wherein the DM candidate is typically a much heavier
(fermionic) neutralino state, this extended model of SUSY offers one with a
much lighter (bosonic) state as DM that can then be produced at the next
generation of $e^+e^-$ colliders with energies up to 500 GeV or so. The ensuing
signal, energing from chargino pair production and subsequent decay, is
extremely pure so it also affords one with the possibility of extracting the
Yukawa parameters of the (s)neutrino sector. Altogether, our results serve the
purpose of motivating searches for light DM signals at such machines, where the
DM candidate can have a mass around the electroweak scale.
