Add amount to employee referral bonus

Summary: We are adding a secondary bonus amount depending on the candidate hired that I want to add on with a report

Content (required): So, we have a referral bonus amount on the requisition, but sometimes, depending on who is hired, the employee could get an extra bonus. I want to put this into a formula. I have tried this and it's not working:

WHEN "Candidate Flex Fields"."UDF32" is 'Yes' THEN "Requisition Budgeting"."Employee Referral Bonus Amount" + 500 ELSE "Requisition Budgeting"."Employee Referral Bonus Amount" END

I'm getting a syntax error but not sure why. I've tried () around things I thought needed it but it isn't working.