MS List Validation and action

I have two columns in a List. The first column is called 'Status' and it contains a dropdown list. The second column is called 'RCA.' I want to set up a validation rule that requires users to update the 'RCA' column before they can select 'Completed' from the 'Status' dropdown. Once they have updated the 'RCA' column, they will be able to update the 'Status' column as completed,Without adding RCA they can't update the status column as Completed

I have added Below validation formula on Status colum

=IF(AND(Status="Completed", ISBLANK([Resolution Summery])), FALSE, TRUE)