Just after your SendChatMessage(), have some variables remember the last spell and last event type along with a timestamp. Then just before this, check if the last spell/last event/timestamp matches the current one. If it matches, don't send the chat message.
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Author of Postal, Omen3, GemHelper, BankItems, WoWEquip, GatherMate, GatherMate2, Routes and Cartographer_Routes