Help with Removing Item from Shops

Help with Removing Item from Shops

Hi I'm new to these forum but have been making maps for quite some time and I've encountered a problem in my latest map.

I have an item which, once sold, must be removed from all shops. I have made the item, the shop and the trigger but they do not work for some reason.

The shop works fine, the item works fine, the trigger works EXCEPT removing the item shops.

I have uploaded screenshots of the item and trigger so if someone can tell me why it is not removing then thanks for the help!

TRIGGER:
http://img464.imageshack.us/img464/7477/trigger2ii.png

ITEM:
http://img464.imageshack.us/img464/1290/upgrade4pd.png

not sure but i think the function only works if u also add the item to the shop through triggers.