[Dayrion]

Why don't you format a string and use strcat after formatting it? Like this example:

PHP Code:

CMD:interiorlist(playerid)
{
    if(!IsPlayerAdmin(playerid))
        return 0;
    new sub_str[100],
        principal_str[250];
    foreach(new i : It_Interior)
    {
        format(sub_str, sizeof(sub_str), "ID: %i » %s\n", i, BizInterior[i][i_Name]);
        strcat(principal_str, sub_str);
    }
    Dialog_Show(playerid, NOTHING, DIALOG_STYLE_MSGBOX, "All custom interiors", principal_str, "Ok", "");
    return 1;
}