The following additional two papers should also can help to perform stability analysis by spreadsheets:
Low, B. K. (1996). ¡°Practical probabilistic approach using spreadsheet¡±. Proceedings of Uncertainty in Geologic Environment: from Theory to Practice, ASCE Geotechnical Special Publication, Vol. 2, No. 58, pp. 1284-1302.
Low, B. K., and Tang, W. H. (1997a). ¡°Reliability analysis of reinforced embankments on soft ground¡±. Canadian Geotechnical Journal, Vol. 34, No. 5, pp.672-685.