[AccessD] Max of 20 values

I have a form into which the user enters up to 20 values (measurements in
time). They all default to zero. I'm trying to think of an elegant way to
find the max value among the 20. Create an array and bubble sort it? I want
to call this code on the AfterUpdate of each of these 20 controls so the
control called MaxReading gets a new value if any of the 20 controls goes
higher than the current MaxReading value.

TIA,
Arthur