make sure you have this stuff in a function that loads after the level is loaded

effect_load(mat_normalmap,"normalmap.fx");
mat_normalmap.skill1=float(sun_pos.x);
mat_normalmap.skill2=float(sun_pos.z);
mat_normalmap.skill3=float(sun_pos.y);

you have to save the shader code in a file called normalmap.fx, and this file must be in your game's root directory, not in a subfolder.