Valid If

[StephenSaid]

I have a Button stack where one of the options is always required and the others are optional.

Example options are LIST("A", "B", "C", "D")

Option A is always required. B, C and D are optional and the user can select as many or no options from these.

What expression is required in the Valid If of the column to make all options available for the user and throws an error if they deselect option A?

[StephenSaid · Accepted solution]

This solved my issue.

IF(
  IN( SELECT( Catalogs[catalogID], [master] = "Y" ), [_THISROW].[catalogsLink]),
  TRUE,
  FALSE
)