A very difficult challenge in Numbers

Question

Morning.
I have a Numbers table, that calculates savings for future investments. But the investments take place surprisingly. That means, there are expenditures where no adequote savings has been done. In such case I want to diminish all the other savings proportionally.
Example:
For savings A monthly $100 are put aside. Savings in an amount of $2'000 has been done.
For savings B monthly $200 are put aside. Savings in an amount of $1'000 has been done.
For savings C monthly $50 are put aside. Savings in an amount of $400 has been done.
In summa there are savings in an amount of $3'400. But if now occasionally  $1'000 of investments C must be done, the savings C are
in Minus by $600.
But savings can not be in Minus. Therefore the Minus must be absorbed by the savings A and B proportionally, e.g. A reduces to $1'600 and B reduces to $800.
How can I do that in Numbers.app?
IF (at least a cell is less than 0) THEN (set all these cells to 0 and sum the amounts lesser than 0) THEN (make the ratio of such amounts lesser the 0 to the sum of the positive savings) THEN (diminish all postitive savings by these ratio).
How to achieve this by a valid Numbers formula?
Kind regards, Friedrich

Answer 1

yes - you could use zsh, but why not use builtin ksh (for support)?
I keep all root history files different in discrete files so you don't accidentally have someone that tries to do a command recall on pattern matching - yielding different than expected results.
it's very simple, but has the obvious caviats if you set any particular user's shell to something other than Bourne static linked -
The syntax and variables can be changed to meet your own needs, near the top of my .profile I insert:
if [ ! -z "$TERM" -a -t 0 ] ; then
startdate=`date +%H%M%m%d%Y`
HISTFILE=$HOME/history/.sh_history.$startdate.`who am i|awk '{print $1"." $2}'|tr '/' '_'` ; export HISTFILE
fi
just setup a history directory for each user and they'll log there whenever they have a term