does anyone know of a program or excel add on that will allow me use decision trees to model risk of disease - often referred to as graphical trees- and if so what is the cost regards ann ------------ Ann E Fitzmaurice Dugald Baird Centre for Research on Women's Health Department of Obstetrics and Gynaecology (University of Aberdeen) Aberdeen Maternity Hospital Cornhill Road Aberdeen AB25 2ZL Scotland, UK. Tel. + 44 1224 553876 Fax: +44 1224 404925 [log in to unmask] ([log in to unmask])