Try to use http://wow.gamepedia.com/API_GetItemCooldown and http://wow.gamepedia.com/API_GetItemCount
var itemId = 64488;
var count = wManager.Wow.Helpers.Lua.LuaDoString<int>("return GetItemCount("+itemId+", nil);");
Logging.Write("Count = " + count);
var timeLeft = wManager.Wow.Helpers.Lua.LuaDoString<double>("local startTime, duration, enable = GetItemCooldown("+itemId+"); return startTime + duration - GetTime();");
Logging.Write("Item Cooldown time left (seconde) = " + timeLeft);