Problem using last function in calculated item

[Zapper]

Hi All,
I have an item key which work fine. But when i try to use it as calculated item and i use the formula below it says "not supported". Is there anything wrong with the formula.

last("myStuff["java-query:name=queryCounterBean,type=QueryCounterResou rce,attribute=queryCounter","{$My_PORT}"]")/30

I do have a trigger for this which also works fine.

Tailing server logs:
error: Can not evaluate function [last(type=QueryCounterResource,attribute=queryCoun ter"])]: item [hostname:jmx["java-query:name=queryCounterBean] not found

[nelsonab]

You might need to escape some of your quotes, or get rid of some, as it's hard to figure out what's nested and what's not right now

try this:

last(myStuff["java-query:name=queryCounterBean,type=QueryCounterResou rce,attribute=queryCounter","{$My_PORT}"])/30

[Zapper]

Thanks nelsonab for your reply. Now i am getting "error: Invalid first parameter in function"on the server log

[Zapper]

It works fine now. Had to use \ in front of all the double quotes