Google sheets How to create a custom function - google-sheets

Question

I have two sheets
Sheet1
and sheet2
What I want to do is one by one copy the values of each row from sheet 1 to sheet 2. whenever one row is copied from sheet1 to sheet2 (i.e values from cell A to F). the cell G2 and H2 (in sheet2) get values ( based on multiple different formulas filter function, pivit tables etc from other sheets ) When I get the updated values in sheet 2 I want to copy the values form G2 and H2 to the respective row back in sheet 1
basically I want to use the sheet2 as a custom function where cell A2, B2, C2, D2, H2, F2 are inputs and cell G2 and H2 are outputs.
I tried using macros but what is required is a combination of both Absolute and Relative referencing and that doesn't seem to be possible
gif of the process I am doing manually

Answer 1

Did it with appscript and menue items
function onOpen() {
var ui = SpreadsheetApp.getUi();
// Or DocumentApp or FormApp.
ui.createMenu('AERON')
.addItem('Calculate Single Cabnets', 'menuItem1')
.addSeparator()
.addItem('Calculate Multiple Cabnets', 'menuItem2')
.addToUi();
}
function menuItem2() {
var sheet = SpreadsheetApp.getActiveSheet();
var selection = sheet.getSelection();
if(selection.getActiveRange().getA1Notation()==null)
ui.alert('No range selected');
else{
//get the inputs
var sheetname = SpreadsheetApp.getActiveSheet().getName();
// SpreadsheetApp.getUi().alert(sheetname);
var range = SpreadsheetApp.getActiveSpreadsheet().getRange(selection.getActiveRange().getA1Notation());
var input = range.getValues();
var ac = SpreadsheetApp.getActiveSpreadsheet().getActiveRange()
SpreadsheetApp.getUi().alert(ac);
// get sheet name
sheetname = SpreadsheetApp.getActiveSheet().getName()
const numRows = ac.getNumRows();
for (let i=1; i<= numRows;i++ ){
var cell = ac.getCell(i, 1).offset(0, 0,1,6).getA1Notation();
var cell1 = ac.getCell(i, 1).offset(0, 7,1,2).getA1Notation();
// SpreadsheetApp.getUi().alert(cell + " " +sheetname + " " + cell1);
single_row(sheetname, cell, cell1 );
}
SpreadsheetApp.getUi().alert("All values updated")
}
}
function single_row(sheetName, inputRange, outputRange ) {
var fnSheetName = "Main";
var fnInputRange = 'A2:F2';
var fnOutputRange = 'G2:H2';
var input = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName).getRange(inputRange).getValues();
SpreadsheetApp.getActiveSpreadsheet().getSheetByName(fnSheetName).getRange(fnInputRange).setValues(input);
var output = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(fnSheetName).getRange(fnOutputRange).getValues();
SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName).getRange(outputRange).setValues(output);
}
This creates a menue item on the top which one by one copies the values to the other sheet then copies the result back