Recording a high value from another cell

I have a spreadsheet that is automatically updated from another program I use.

Cell AD5 has a value that constantly changes (up and down) after each update from the program.

What I want to be able to do if it is possible, is to have another cell (AF5) show the HIGHEST figure ever recorded in cell AD5...and adjust accordingly each time AD5 hits it's highest ever amount.

eg, lets say AD5 starts with 100....it then drops to 98....AF5 retains 100.....AD5 then changes to 102....AF5 changes to 102....AD5 drops to 96....AF5 would retain 102...etc

The figure returned in cell AF5 is then used as a trigger in another column/cell.

I could use additional cells apart from AF5 if it is necessary.

Possible?

Many thanks for taking the challenge.
Cheers
Hammer