[3 cards of your choice = 1 random card]

prontera,150,150,6   script	 Sample	100,{
	getinventorylist;
	for (.@i = 0; .@i < @inventorylist_count; .@i++) {
		if (getiteminfo(@inventorylist_id[.@i], 2) == 6) {
			.@menu$ = .@menu$ + "- " + getitemname(@inventorylist_id[.@i]) + " x"+@inventorylist_amount[.@i]+":";
			.@cards[getarraysize(.@cards)] = @inventorylist_id[.@i];
		}
	}
	
	.@i = 0;
	
	mes "Please select 3 cards...";
	while (.@i < 3) {
		if (getarraysize(.@c)) {
			mes "> 1x " + getitemname(.@c[.@j]);
			.@j++;
		}
		.@s = select(.@menu$) - 1;
		.@c[getarraysize(.@c)] = .@cards[.@s];
		.@i++;
	}
	mes "> 1x " + getitemname(.@c[.@j]);
	next;
	mes "Are you sure you want to trade these cards?";
	if (select("~ Yes:~ No") & 2) end;
	
	for (.@i = 0; .@i < getarraysize(.@c); .@i++)
		delitem .@c[.@i], 1;
	
	set @Rand,rand(4001,4699);
        next;
        getitem @Rand,1;
        mes"Congratulations!!.... you received";
        mes "^CC99CC"+getitemname(@Rand)+"^000000";
	close;
}

 I have a little bit of customization, you try this. 

thx @Patskie