What is syntax and best way to force an Apex form field entry to be all uppercase?

Using free cloud instance if Oracle DB and Apex

I need to insure a text field entry (lastname) is all uppercase by changing the entry if user enters mixed characters to all upper before insertion into database. I see the "Computation" feature in page designer, but found no useful help documentation on syntax. Should I use an Expression type? Which language? If say PL/SQL what is the syntax to put in the expression for an UPPER function. That is, is there an identifier required to the left of the assignment operator? Would that be the name of the form field? How about the identifier to reference the input field?