Coll again; How to tell how many items are in it?

Hi, it's me again, still with my coll object...
If someone is around and has a suggestion, I would be very thankful... I just don't seem to get the hang of working with boxes...

I am trying to build a patch that will take some pairs of items and add them to a coll object, or remove them from it. I would like to know when the coll is empty, but I haven't found the way to do it reading the coll object help files.
So I tried building a separate counter that keeps track of the items that are sent to be added or deleted. But it doesn't work, because I am not able to verify if the item to add or delete is actually in the coll or not (there could be a request to remove something that was already removed from the coll).
Is there a way to get the coll object to tell me how many items it has?

I will attach my test patch but it is very messy and I don't think it is necessary to look at it.

Thanks
Julieta