A less technical answer might be to add this condition at the bottom of your posts:
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This offer to trade is limited to registered FT members of more than six months or 300 posts. Those who respond without meeting this criteria will not receive the item in question; you will, however be automatically subscribed to free money-saving newsletters by email! These include savings on mortgages, farm sex videos, organ enhancement, herbal viagra, and getting out of debt plus thousands more! In addition, you will receive an opportunity to help victims of political oppression in Nigeria and make some money at the same time!
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Just a thought.
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-alan in sitges, home of the new, improved
Si-Re-Do
[This message has been edited by alanw (edited Dec 19, 2003).]