Hi @Erwin S ,
We understand you would like to decline part of recurring meeting automatically, is it right?
If so, plelase kindly understand the recurring meeting is actually a complete series in Outlook, which means we may not be able to accept or decline part of it only in Outlook now. For your requirement of this feature, it's suggested to vote this idea in outlook uservoice, which is the Official channel for the Outlook team to collect more good ideas from users and help improve our product.
And for your currently normal use, I'm afraid you need to delete them manually. As a tip, in order to save time, you could try to press Ctrl key to select multiple occurrences you would like to delete.
Hope that would be helpful to you.
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