Using Apex 18.1 I need to create a custom link for only a pie chart slice?

Link should only work when I click on green slice, but not on grey. Actually on grey I need a different link (to different page with different items).
To simplify my question, I have a pie chart which displays the count of 3 items A, B, C.
I need to be able to click on the chart on pie slice A and redirect to a page in the application, and click on pie slice B and redirect to ANOTHER page in the application.
Both pages also take different items as input.
Using the chart link option I can set a link for the entire chart, but not for a specific chart pie slice only.
I also tried to build my link in the pie chart SQL:
select
case when item = 'A' then f?p='||:APP_ID ||':10:'||:APP_SESSION||'::NO:RP:P10_CODE_ID:'||code_id
_when item = 'B' then f?p='||:APP\_ID ||':11:'||:APP\_SESSION||'::NO:RP:P11\_TEST\_ID:'||test\_id_
_when item = 'C' then ''_
_end as link,_
...
but how can I reference this ?
Thanks for any pointers.