Length of Service calculation OTBI

Summary

Calculation of LOS based on either Current Date or Termination Date for former employees.

Content

I am looking to calculate an individual's length of service based on Work Relationship Start Date (so can't use the inbuilt measure as that goes on Seniority date which for us is sometimes significantly beforehand). Have done for existing staff based on Current_Date and start date however when looking at all records I come unstuck with termination dates as that calculates based on them not having left.

Effectively, I am looking for code to do: If Termination Date is NULL or >=Current Date then calculate Current Date to Start Date but if Termination Date < Current Date then calculate Termination Date to Start Date.