function onFormSubmit(event) {
try {
// event is the event object { range: {}, namedValues: {}, values: [], authMode: enum, triggerUid: uid }
let parent = e.range.getSheet().getParent(); // parent spreadsheet
let sheetB = parent.getSheetByName("Sheet B");
// get some table of hours limit (total unknown to me what that is)
let hoursLimt = parent.getSheetByName("Some sheet").getRange(1,1,10,1).getValues();
// "respondant" is in column A of the hoursLimit table and event.values[0]
// look up respondant in the lookup table
let respondant = hoursLimit.find( row => row[0] === event.values[0] );
if( respondant === undefined ) throw "Respondant ["+event.values[0]+"] not found";
sheetB.appendRow(event.values);
SpreadsheetApp.flush(); // insure new row has been added
// assume respondent[1] is the limit (H) and event.values[3] (D) is the form value
// getRange(sheetB.getLastRow(),7) is column G of the new row
sheetB.getRange(sheetB.getLastRow(),7).setValue(respondant[1]-event.values[3]);
}
catch(err) {
console.log(err);
}
}