Many Diabetic chocolates have the sugar replaced with artificial sweeteners such as saccharin and sugar alcohol called sorbitol . But as the bulkiness of the sugar is replaced with soya flour and ground nuts.However these replacements are not completely satisfactory. Store brought chocolate chips may contain higher amount of cocoa butter than the plain dark chocolate ones you made with splenda. If you can add an amount of cocoa butter(5-15%) of the total batch weight of the chocolate mixture; and that may partially help in increasing the viscosity of the chocolate to help maintain its integrity in the chocolate chip cookie application. Another thing is to blend splenda half with finely ground almonds, then add the nut /splenda compositions to the dark chocolate and , as that will help provide the body to minimize the fluidization of sugarless chocolate when exposed to oven heat. If the resulting cookie does appear to be less sweeter you can add more splenda to the cookie recipe to maintain the desired taste. Good Luck! Roy