INPUT command OK and Cancel parameters

[Bob Frazee]

Page 551 in Prime User Manual
INPUT
Syntax: INPUT(var [,"title", "label",
"help", reset]);
Opens a dialog box with the title text title, with one
field named label, displaying help at the bottom and
using the reset value if "Shift" "Esc" is pressed.
Updates the variable var if the user taps "OK" and
returns 1. If the user taps "Cancel", it does not update the
variable, and returns 0.

Where can I capture the above OK and Cancel values to test if they have been selected?
rcf