Hi all, I wish to thank all of you that replied to my enquiry. Lots of good responses and ideas. Cheers Rolf Rolf Tschudin Contractor, NMR support, Bldg. 5, Rm. B2-41 National Institutes of Health Bethesda, MD 20892 Tel. 1 301 496 2692 e-mail: tschudin@nih.gov