This procedure sets the PICT ID used for the display of the named button.
The first parameter is the external area name.
Second parameter is PICT resource ID of up button.
Third parameter is PICT resource ID of down button
If you use a negative value for one of those ID parameters, the current value will be kept.
The last parameter is the PICT ID resource of disabled button. If you pass 0, the disabled button won't be displayed. If you pass -1, the button will be displayed with a white pattern over. If you pass a negative value under -1, the previous value will be kept.