Gina Welcome to the network. Just keep posting questions. We'll try to provide you with the answers. Best of luck with your studies Chris Packham EnviroDerm Services ~~~~~~~~~~~~~~~ Please remove this footer before replying. For list archives and documents, go to http://www.jiscmail.ac.uk/lists/occ-health.html for list archives For jobs in Occupational Health, go to http://uk.groups.yahoo.com/group/OHJobs/