its really simple just do loop with somehing like this in it
NPC Code:
if (tiles[x,y]=thetilenumber) tiles[x,y]=theothertilenumber;
like maybe:
NPC Code:
timeout=0.05;
if (tiles[x,y]=0x00F5) tiles[x,y]=0x01CD;
else if (tiles[x,y]=0x01CD) tiles[x,y]=0x01CE;
else if (tiles[x,y]=0x01CE) tiles[x,y]=0x00F5;
(i just picked random numbers i dont no what they r xD)