[[XST]O_x]

pawn Code:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(!strcmp(cmdtext,"/example"))
    {
        new Float:p_Pos[3]; GetPlayerPos(playerid,p_Pos[0],p_Pos[1],p_Pos[2]);
        if( (p_Pos[0] == /* The X pos*/) && (p_Pos[1] == /*The Y pos*/) && (p_Pos[2] == /*The Z pos*/) )
        { 
            //Command applys here.
        }
        else SendClientMessage(playerid,-1,"You're not in the correct positions!");
        return 1;
    }
    return 0;
}

But to be in the exact position you need to be pretty damn accurate.