[AndySedeyn]

What you have to do is simply change the SkillLevel of a certain player.
Maybe you should try to make a command to start with..

ZCMD

pawn Code:

CMD:skill(playerid, params[])
{
    SetPlayerSkillLevel(playerid, 0, 5); // The 0 here stand for the Skill: WEAPONSKILL_PISTOL
    return 1;
}

Strcmp

pawn Code:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(strcmp(cmdtext, "/skill", true) == 0)
    {
        SetPlayerSkillLevel(playerid, 0, 5);
        return 1;
    }
    return 0;
}

These are the ID's of the Weapon skills:

pawn Code:

0 - WEAPONSKILL_PISTOL
1 - WEAPONSKILL_PISTOL_SILENCED
2 - WEAPONSKILL_DESERT_EAGLE
3 - WEAPONSKILL_SHOTGUN
4 - WEAPONSKILL_SAWNOFF_SHOTGUN
5 - WEAPONSKILL_SPAS12_SHOTGUN
6 - WEAPONSKILL_MICRO_UZI
7 - WEAPONSKILL_MP5
8 - WEAPONSKILL_AK47
9 - WEAPONSKILL_M4
10 - WEAPONSKILL_SNIPERRIFLE

The format of the function: SetPlayerSkillLevel is:

Code:

SetPlayerSkillLevel(playerid, ID_WEAPONSKILL, Skill_level);