I don't know if this is what you mean, but you can find similar commands by reading the fine manual for this (which is
doc/script_commands.txt):
*countitem(<item id>

*countitem("<item name>")This function will return the number of items for the specified item IDthat the invoking character has in the inventory.mes "[Item Checker]";mes "Hmmm, it seems you have "+countitem(502)+" apples";close;Like 'getitem', this function will also accept an 'english name' from thedatabase as an argument.If you want to state the number at the end of a sentence, you can do it byadding up strings:mes "[Item Checker]";mes "Hmmm, the total number of apples you are holding is "+countitem("APPLE");close;
Edit: Dang, if you're allowed to have apples only you should check this other function:
*getinventorylist;This command sets a bunch of arrays with a complete list of whatever the invoking character has in its inventory, including all the data needed to recreate these items perfectly if they are destroyed. Here's what you get

inventorylist_id[] - array of item ids.@inventorylist_amount[] - their corresponding item amounts.@inventorylist_equip[] - whether the item is equipped or not.@inventorylist_refine[] - for how much it is refined.@inventorylist_identify[] - whether it is identified.@inventorylist_attribute[] - whether it is broken.@inventorylist_card1[] - These four arrays contain card data for the@inventorylist_card2[] items. These data slots are also used to store@inventorylist_card3[] names inscribed on the items, so you can@inventorylist_card4[] explicitly check if the character owns an item made by a specific craftsman.@inventorylist_expire[] - expire time (Unix time stamp). 0 means never expires.@inventorylist_count - the number of items in these lists.@inventorylist_bound - whether it is an account bounded item or not.This could be handy to save/restore a character's inventory, since no other command returns such a complete set of data, and could also be theonly way to correctly handle an NPC trader for carded and named items who could resell them - since NPC objects cannot own items, so they have to store item data in variables and recreate the items.Notice that the variables this command generates are all temporary, attached to the character, and integer.Be sure to use @inventorylist_count to go through these arrays, and not 'getarraysize', because the arrays are not automatically cleared between runs of 'getinventorylist'.
Just check that @inventorylist_count is 1 and that @inventorylist_id[0] is the Apple item ID.