
Hi @Wande
Per my research, currently there is no ootb method to meet your requirement directly, we could only edit or add more through editing the Choice column.
What's more, if you want when "Project ABC" is selected, the value in column B could only be :
- 15th Dec **(Date*) - Discussion with vendor (activity date description )
- 17th Dec (Date) - Call suppliers (activity date description)
- 25th Dec (Date) - Enjoy Xmas (activity date description)*
you need to use power apps. For more information, you could refer to:
https://techcommunity.microsoft.com/t5/sharepoint/list-of-choice-for-one-column-based-on-another-column/m-p/3383848
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