Case statements to capture past and future events

ForSly

I am trying to write a case statement  to calculate workflow events  based on job applicants recruiting process.

Basically when a prospective candidate applies for particular job  the recruiter   can interview them for the job they applied for or  a recruiter might assign  an  applicant to a different job from which hey had applied for.

The problem I am facing is that if an applicant applied for a job in say 1/15/2019 and a recruiter decide to assign them a different job on 2/1/2019 at which point say the applicant had gone through  application review, testing and interview as part of workflow for the first application during month of January 2019 and say in February 2019 they were offered a job, I need to be able to show that they were offered a job in January when I run my report between 01/01/2019 -01/31/2019. I am trying to solve this using case statement , please advise.