Is it possible to have a list of tasks each with a formula to track progress in percentage based on other subtasks? The result will look like this:

* [ 30%] Project Name
** [ 50%] Task A
** [ 10%] Task B

This is what my formula in lisp will look like:

* [(format "%3d" (+ (* TASKA 0.5) (* TASKB 0.5) ))%] Project Name
** [(format "%3d" (setq TASKA 50)%] Task A
** [(format "%3d" (setq TASKA 10)%] Task B


All I need to do is evaluate the code in org-mode to get the result.
Is this possible?

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Asif