I assume that you've read the helpsheet on this one?
http://www.hmrc.gov.uk/helpsheets/hs293.pdf
there are built in examples which should help you.
kind regards,
Shaun.
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Shaun
Responses are not meant as a substitute for professional advice. Answers are intended as outline only the advice of a qualified professional with access to all relevant information should be sought before acting on any response given.