Matching on one of two possibly interacting exposures can increase power and efficiency to estimate multiplicative interactions in case-control studies. We recently introduced the concept of flexible matching strategies with varying proportions of a dichotomous matching factor among controls to further increase power and efficiency. In order to facilitate the application of this concept, we developed a computer program which provides estimates of power and efficiency varying the proportion of the matching factor in controls over all possible values from 1 to 99%. The program allows one to estimate the effect of frequency matching on power and efficiency to study multiplicative interactions and to assess the optimal prevalence of the matching factor in selected controls for a given scenario which often differs from the prevalence in cases (aimed at in traditional 'fixed' frequency matching). Our program will strongly facilitate assessing the benefits of matching and flexible matching strategies in case-control studies addressing multiplicative interactions, including gene-environment interactions.