Use customCellEnterPost for custom behavior when focus comes into a cell, after the default Planning logic runs. This code runs when users click in a cell, after the Planning default logic if customCellEnterPre and the default logic return True. If they return False, this function is disabled.
SampleValidateData.js includes an example for customCellEnterPre that you can use for customCellEnterPost. The example displays a message prompting the user to enter supporting detail clicking in specific cells.