This theoretical Letter addresses the non-linear optical properties of a series of substituted dimethylaminophenylethylenyl-indolino[2,1-b]oxazolidine derivatives, which were recently shown to behave as multiaddressable NLO switches. The influence of the chemical nature of the substituent on the static and dynamic first hyperpolarizability, as well as of its grafting location, is investigated by using various semi-empirical and high level ab initio schemes. It is found that a para-substitution on the indolinic skeleton with a [(N,N-1,3-dimethylpyrimidine-2,4,6-trione)-5-yl]methylidenyl group should increase by 75% the efficiency of the switches.