try this and sorry for my english.
prontera,158,326,4 script Event Coin Changer 822,{
mes "[Event Coins Changer]";
mes "Hi ^ff8000"+strcharinfo(0)+"^000000, I can exchange your coins to higher coins.";
mes "25 Poring Coins(PC)+ = 1 Bronze Coin(BC)";
mes "5 Bronze Coin(BC) = 1 Silver Coin(SC)";
mes "5 Silver Coin(SC) = 1 Gold Coin(GC)";
mes "5 Gold Coin(GC) = 1 Platinum Coin(Plat)";
mes "What would you like to do?";
next;
switch(select("PC to BC","BC to SC","SC to GC","GC to Plat",)) {
case 1:
mes "How many you want to exchange?";
next;
input .@count;
if (.@count == 0) close; // optional: if player enter 0 script will terminate
if (countitem(7539) < .@count*25) goto L_NE;
delitem 7539,.@count*25;
getitem 673,.@count;
close;
case 2:
mes "How many you want to exchange?";
next;
input .@count;
if (.@count == 0) close; // optional: if player enter 0 script will terminate
if (countitem(673) < .@count*5) goto L_NE;
delitem 673,.@count*5;
getitem 675,.@count;
close;
case 3:
mes "How many you want to exchange?";
next;
input .@count;
if (.@count == 0) close; // optional: if player enter 0 script will terminate
if (countitem(675) < .@count*5) goto L_NE;
delitem 675,.@count*5;
getitem 671,.@count;
close;
case 4:
mes "How many you want to exchange?";
next;
input .@count;
if (.@count == 0) close; // optional: if player enter 0 script will terminate
if (countitem(671) < .@count*5) goto L_NE;
delitem 671,.@count*5;
getitem 677,.@count;
close;
}
L_NE:
mes "You don't have that coin enough.";
close;
}