The susceptibility of iterated block ciphere to differential cryptanalysis is minimised by usng s-box functions with how differential unifromity. We extend the idea of differential uniformity to s-boxes with array inputs, giving a unified perspective from which to approach existence and construction problems for highly nonlinear functions. Perparties of 213 diffrentially m-uniform functions are derived, two constructions are given and relationships with known ID PN and APN function are demonstrated