SOLVE function better solution - google-sheets

Question

I have a spreadsheet where a lot of cells are multiplied with a CONSTANT value and added and the result (SOLL) differs from the expected (IST) value and the only way I was able to find, was to make 10 iterations modifying each time the CONSTANT value till the SOLL and IST are pretty equal.
My method looks too stupid and I am just asking a beautiful and intelligent way to solve it...
thanks
function costante()
{
var ss = SpreadsheetApp.getActiveSpreadsheet(); //spreadsheet "options"
SpreadsheetApp.setActiveSheet(ss.getSheets()[0]); //sheet nr.1
var sheet = SpreadsheetApp.getActiveSheet();
for(var i=0; i<10; i++){
var dataRange = sheet.getRange("o5:o5"); //marge ist
var mist = dataRange.getValues();
var dataRange = sheet.getRange("o4:o4"); //marge soll
var msoll = dataRange.getValues();
var dataRange = sheet.getRange("n1:n1"); //costante
var costante = dataRange.getValues();
var minus = 1;
if(mist - msoll < 0) { minus = -1};
costante = mist / msoll * minus * costante;
sheet.getRange("n1:n1").setValues([[costante]]);}
}

Answer 1

Maybe what you want, assuming your "lot of cells" are in A1:A10 and the IST value is in E1 is:
=E1/sum(A1:A10)
but please note the tag wiki.

Answer 2

thanks, I was first surprised by the simple method and I checked it:
10 values and their addition gives for instance = 10 (sum(a1:a10))
the IST value that I would like to have is 500 (E1)
E1/sum(A1:A10) = 500/10 = 50 = C (COSTANTE)
E1 = Sum(A1:A10) x C
if I multiply each A(y) value with 50, I have 500 and the proposed formula would perfectly work
BUT I forgot to mention that the values of A(y) are formulas that include already my COSTANTE it means that in reality each A(y) value is a formula that contains C
E1 = Sum( A(y) x C ) x C
a) for that reason the solution proposed does not give the needed value, and I was obliged to repeat the calculation ca.10 times
b) I also added a delay of 1 second because I was not sure if the spreadsheet is able to calculate so fast (please tell me if it is necessary)
c) and I said that if the result is +/- 2 from expected value, to stop to calculate
It works but is still not beautiful...
function costante()
{
var ss = SpreadsheetApp.getActiveSpreadsheet(); //spreadsheet "options"
SpreadsheetApp.setActiveSheet(ss.getSheets()[0]); //sheet nr.1
var sheet = SpreadsheetApp.getActiveSheet();
var dataRange = sheet.getRange("o5:o5"); //marge ist
var mist = dataRange.getValues();
for(var i=0; i<20; i++)
{
var dataRange = sheet.getRange("o4:o4"); //marge soll
var msoll = dataRange.getValues();
var dataRange = sheet.getRange("n1:n1"); //costante
var costante = dataRange.getValues();
var diff = msoll - mist;
if(diff < -2) { costante = costante * 1.005;}
else if (diff > 2) { costante = costante * 0.995;}
else {return;}
sheet.getRange("n1:n1").setValues([[costante]]);
Utilities.sleep(1000); //wait 1.5sec
}
}