Here is how I would do it:

Just have the input box open when the check box is checked
Names Default To Here( 1 );
nw = New Window( "check boxes",
	V List Box(
		H List Box(
			redCkBox = Check Box(
				"By Check (bill me later)",
				If( redCkBox << get == 1,
					rTxEditBox << visibility( visible );
					rtb << visibility( visible );
				,
					rTxEditBox << visibility( collapse );
					rtb << visibility( collapse );
				)
			),
			rTxEditBox = Number Edit Box( 0.0 ),
			rtb = Text Box( ".00" )
		),
		H List Box(
			greenCkBox = Check Box(
				"By Credit Card",
				If( greenCkBox << get == 1,
					gTxEditBox << visibility( visible );
					gtb << visibility( visible );
				,
					gTxEditBox << visibility( collapse );
					gtb << visibility( collapse );
				)
			),
			gTxEditBox = Number Edit Box( 0.0 ),
			gtb = Text Box( ".00" )
		)
	)
);
rTxEditBox << visibility( collapse );
rtb << visibility( collapse );
gTxEditBox << visibility( collapse );
gtb << visibility( collapse );
 
					
				
			
			
				
	Jim