# set terminal svg size 600,400 dynamic enhanced fname 'arial'  fsize 10 mousing name "fillbetween_3" butt solid 
# set output 'fillbetween.3.svg'
set style fill   solid 1.00 noborder
set style data lines
set title "Fill area between two curves (above/below)" 
set xrange [ 250.000 : 500.000 ] noreverse nowriteback
plot 'silver.dat' u 1:2:($3+$1/50.) w filledcurves above title 'Above',                '' u 1:2:($3+$1/50.) w filledcurves below title 'Below', 	       '' u 1:2 lt -1 lw 2 title 'curve 1', 	       '' u 1:($3+$1/50.) lt 3 lw 2 title 'curve 2'