Your device driver should use the DriverProc system messages for its installation and configuration routines. These messages are described in the documentation for the Microsoft Windows Software Development Kit.
The Joystick applet records the calibration settings in the SYSTEM.INI file, under the [Joystick.Drv] section. After loading the joystick driver, MMSYSTEM reads the calibration information from SYSTEM.INI and sends it to the joystick driver with the JDD_SETCALIBRATION message.
The Joystick applet lists the calibration settings in the following format:
JoyCaln=xBase xDelta yBase yDelta zBase zDelta
Each number is a two-byte hexadecimal value. For example, a system with a single two-dimensional joystick might have the following entry:
[Joystick.Drv]
JoyCal0=0e64 0133 0c30 00f0 0000 0000
JoyCal1=0000 0001 0000 0001 0000 0001
To supply a different calibration applet than Joystick, your applet should record the calibration information in this format.