Hi
If you just need a simple report you can probably use a column report. Make a column layout (View/Column Setup) that shows the UDF (and any other details you need) then search for the contacts (sort eg. by company name) and use file /print column report tick the box Print Totals For Numeric User Defined Fields
This should do the trick. If not you'll probably need to use the built in reportsmith software - but I'm afraid I can't explain how to use that here! (it would need a couple of pages)
Hope this helps, if not tell me a bit more about what your trying to achieve.
Ian Wallace
CABC, Newbury