Hello everyone, Thanks to all of you who answered my questions. The replies I got greatly stimulated my thinking in that area. If you are interested in seeing what some of the answers I received look like, just email me. Best Regards Francois Quesnel Department of Land Resource Science University of Guelph Guelph, Ontario, N1G 2W1 Vox: (519) 824-4120 x8593 Fax: (519) 824-5730 Email: fquesnel@lrs.uoguelph.ca