In this paper, we have extended the concept of contraction by introducing DContraction defined on a family of = of bounded function . Also, a new notion of fixed function has been extended G-metric space. Some fixed theorems with illustrate examples have also been given to verify the effectiveness of our result. In 2019, Vishal et. al [3] presented some fixed function theorems using the notion of fixed function and D-Contraction in complete metric space. Following this concept, a sequence is constructed in G-metric space with three different dose function which converges to a fixed function. An application based on the best approximation of treatment plan for tumor patients by splitting DDC matrix into three components with three dose functions.