[Twizted]

pawn Код:

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if (newkeys & KEY_FIRE) {
        //change KEY_FIRE to the desired key —  https://sampwiki.blast.hk/wiki/Keys
        //Code to perform if they is pressed.   
    }
    return 1;
}

Something like this is what you should be looking for (I didn't compile it, but it should be working). I suggest you read through Kraeror's first link though.