I am trying to create a field dependency which makes one field required when another is marked as yes. The field that I am trying tomake required (If_IBO_Renewal_Date__c ) is a date field, not a picklist, so I am unable to write a formula wtihout errors.  Any thoughts on how to structure this?  My current formula is below. Thanks!

AND(OR( ISPICKVAL( IBO__c ,"Yes"), (OR((
ISPICKVAL(If_IBO_Renewal_Date__c , "" ))))))