Pilot Logbook

Hi everyone, need some help with an excel formula. Refer to attachment:

Column A is where I enter the date for a flight. Column X is the number of ILS approaches performed on that flight. Cell X4 is where I input the last date I completed an ILS and cell X5 calculates when the next one is due.

Instead of having to input the date manually into X4 I would like a formula that scans column X for the most recent entry and returns the date that it occured from column A.

Im sure it can be done but have no idea how to do it.

Cheers in advance.