Current maximum is 64 threads per single Analysis window.
But you can run two or more Analysis windows in parallel and then they will use N * 64 threads where N is number of analysis windows.
Plus don't forget that Charts use in separate threads too.
Unless you are doing some really super heavy math in your formula you are not likely to be limited by CPU speed but by RAM bandwidth.
I can easily increase the limit in the program from 64 threads to 128 threads, but I really doubt if you would see any gain, as a) you are likely to be limited by RAM bandwidth and b) you only have 64 true cores. Hyperthreading (SMT) does not count as "real core".
See KB article:
Also as @Pietro wrote, Windows OS by itself limits the number of threads to 64 per group and I am afraid that this would impact real performance too and the program might not be able to run more than 64-threads even if it asked for.
You might need to check yourself. Run two Analysis windows and run Microsoft Process Explorer, it will display all threads in process Properties / Threads window.