Rather obviously @slider is only called when a slider is modified from outside the JSFX code.
You might try to do a function that contains what you want to do in @slider and do something like
Code:
@init
function do_slider() (
parameter1 = slider1;
);
@slider
do_slider();
@gfx
slider1 != gfxslider ? (
slider1 = gfxslider;
do_slider();
);