Google Sheets - search and work with data?

Question

Google Sheets

Hello. Tell me how you can implement such functionality in Google spreadsheets:
There are 3 pages: Main, Income, Expenses
The main table displays a table with columns: Product size, plan (qty), product (qty)
In income and expense: Date, Size items (
Drop -down list with elements from the main page), quantity On the main page, next to this product (which we selected in the drop-down list), calculations were made if the income was increased, if the consumption was reduced.
The main problem I have is how to do something on the general page; for each element, it scanned the income-expense, found its size (there will be more than one line) and added / subtracted everything that it finds.
I tried my best to convey my thoughts. At least tell me if it is possible to implement this and in what direction to look?

Answer 1

Track onEdit ()
Here is a template that can be used:

function onEdit(event) {
  //Возникает при изменении ячейки
  var ss = event.source.getActiveSheet();//Текущий лист
  	var address = event.range.getA1Notation().toUpperCase();//Адрес ячейки
  var row = event.range.getRow();							//Номер строки
  var col = event.range.getColumn();						//Номер столбца
  var newValue = event.value;								//Новое значение
  var oldValue = event.oldValue;							//Старое значение
  
  if (["Лист1","Лист2"].indexOf(ss.getName())==-1) return;	//Указываем на каких листах должен работать скрипт
  
  //Что-то делаем...
  };