Return Corresponding Data To Latest Date

I am trying to use a function to search for a particluar value (e.g., ssn) in one column and return the "InDate" in another column. I thought this would be easy, but I'm having considerable trouble. When I do manage to get a value returned, it's the wrong value. I need to return the most recent "InDate" for the ssn that I search for. The button on the " Lookup" sheet is to sort the InDate column descending so that the Excel function will start with the most recent date when it searches. I've tried Lookup and and just about every other similar function with no luck. I originally wanted to search for a ssn and return the information for the last 5-10 most recent visits, but gave up on that long ago.