  We propose a theoretical/computational protocol based on the use of the
Ground State (GS) Path Integral (PI) Quantum Monte Carlo (QMC) for the
calculation of the kinetic and Coulomb energy density for a system of $N$
interacting electrons in an external potential. The idea is based on the
derivation of the energy densities via the $N-1$-conditional probability
density within the framework of the Levy-Lieb constrained search principle. The
consequences for the development of energy functionals within the context of
Density Functional Theory (DFT) are discussed. We propose also the possibility
of going beyond the energy densities and extend this idea to a computational
procedure where the $N-1$-conditional probability is an implicit functional of
the electron density, independently from the external potential. In principle,
such a procedure paves the way for an {\it on-the-fly} determination of the
energy functional for any system.
