Backstab Skill Custom Effect

[dreinor 5]

hi.. can someone help me.. i want to make the skill of Rouge Backstab to be useable even if the target is facing the caster, but the damage will be reduced by 75% and is now affected by hit rate.. would this be possible? here is the code for backstab skill..
 

case RG_BACKSTAP:

{

uint8 dir = map->calc_dir(src, bl->x, bl->y), t_dir = unit->getdir(bl);

if ((!check_distance_bl(src, bl, 0) && !map->check_dir(dir, t_dir)) || bl->type == BL_SKILL) {

status_change_end(src, SC_HIDING, INVALID_TIMER);

skill->attack(BF_WEAPON, src, src, bl, skill_id, skill_lv, tick, flag);

dir = dir < 4 ? dir+4 : dir-4; // change direction [Celest]

unit->setdir(bl,dir);

}

else if (sd)

clif->skill_fail(sd,skill_id,USESKILL_FAIL_LEVEL,0);

}

break;

i tried replacing the code after else if with "skill->attack(BF_WEAPON, src, src, bl, skill_id, skill_lv*.25, tick, flag);" but the skill is not working.. anyone willing to help me on this? thanks..