I have multiple savings accounts, some of which I want to partition into mutiple virtual "subaccounts" that don't merit their own savings account. I want to use org-mode tables to keep track how much money is each subaccount. Given the following table:

#+TBLNAME: trans-150925

| ! | Amount | From       | To         | Subacct     |

|---+--------+------------+------------+-------------|

|   |     50 | Short Term | Inbox      | Bond        |

|   |    200 | Inbox      | Short Term | Bond        |

|   |    120 | Gifts      | Inbox      | Baby Gifts  |

|   |     75 | Short Term | Inbox      | Furnishings |

In this example, I have accounts "Inbox", "Short Term", and "Gifts". Of these accounts, "Short Term" has two subaccounts "Bond" and "Furnishings", and "Gifts" has a subaccount "Baby Gifts". I want to create a function that given a subaccount name, calculates the net amount to be withdrawn/deposited to the subaccount. Note that "Inbox" doesn't have any subaccounts, which I want to use to determine if a given transaction is a withdrawal or deposit to the subaccount.

I have created the following two functions to implement this:

(defun sbr/org-lookup-trans (category date s-name r-name)

  (let* ((table (concat "trans-" date))

         (s-range (format "@I%s..@>%s" s-name s-name))

         (s-col (org-table-get-remote table s-range))

         (r-range (format "@I%s..@>%s" r-name r-name))

         (r-col (org-table-get-remote table r-range)))

    (org-lookup-all category s-col r-col)))

(defun sbr/get-net-subacct (category date)

  (let* ((from-vec (sbr/org-lookup-trans category date "$Subacct" "$From"))

  (to-vec (sbr/org-lookup-trans category date "$Subacct" "$To"))

         (amount-vec (sbr/org-lookup-trans category date "$Subacct" "$Amount"))    

         (from-inbox-ind <indices of all from-vec elements that equal "Inbox">) ; A

       (to-inbox-ind  <indices of all to-vec elements that equal "Inbox">) ; B

       (adds amount-vec[from-inbox-ind]) ; C

       (subs amount-vec[to-inbox-ind]))  ; D

    (calc-eval (if (zerop (length subs))

                 adds

 (concat adds "-" subs)))))

I need help filling in the pseudo code in lines A through D, namely:

1. how to get a list of all indices of elements in a vector that satisfy a predicate?

2. how to reference a vector by a list of indices?

In this example the function should return the following values:

(sbr/get-net-subacct "Bond" "150925") ==> 150

(sbr/get-net-subacct "Furnishings" "150925") ==> -75

(sbr/get-net-subacct "Baby Gifts" "150925") ==> -120

How do I implement the above pseudocode functions? Is there a simpler way to accomplish this task?