2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35574Spacetime singularities in numerical relativity can be avoided by excising a region of the computational domain from inside the apparent horizon. We report on results of such a scheme that is based on using ({\it i}) a horizon locking coordinate which locks the coordinate system to the geometry, and ({\it ii}) a finite differencing scheme which respects the causal structure of the spacetime. With this technique a black hole can be evolved accurately well beyond $t=1000M$, where $M$ is the black hole mass.3 pages, uuencoded gziped ps file including 1 Fig. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/ To appear in the MG7 proceedingsGeneral Relativity and Quantum Cosmologytext