Here is the example JSL from the scripting index (Help==>Scripting Index) on specifying how to reverse the scale
Names Default To Here( 1 );
Open( "$sample_data/big class.jmp" );
gb = Graph Builder(
Variables( X( :height ), Y( :weight ) ),
Elements( Points( X, Y ), Smoother( X, Y ) )
);
gbr = Report( gb );
gbr[axisbox( 1 )] << Reversed Scale( 1 );
Jim