define a global var variable, for example one to be adjusted between -100 and 100 with the default value of 0:
Code:
var variable_to_adjust = 0;

within a function create your panel e.g. on layer 10, the size of the bmap will determine whether a hirozontal or vertical is created:
Code:
your_panel = pan_create(panel_background_bmp, 10):

you can add digits, sliders etc.
Code:
pan_setdigits(your_panel, 0,	15,80,	"Value: %0.f",	panel_font,		1, 		variable_to_adjust);
pan_setslider(your_panel, 0,	125,80,	horiz_slider_bmp, slider_knob_bmp,	-100,100,	variable_to_adjust);

Free world editor for 3D Gamestudio: MapBuilder Editor