function main(){
var ss_url = 'SPREADSHEET_URL';
var ss = SpreadsheetApp.openByUrl(ss_url);
var sheet = ss.getActiveSheet();
var tableRows = ['=VLOOKUP('+SEARCH_KEY+','+RANGE+','+INDEX+', '+IS_SORTED+')'];
sheet.appendRow(tableRows);
Logger.log(sheet.getRange(sheet.getLastRow(), 1).getDisplayValue());
//sheet.deleteRow(sheet.getLastRow()); // delete the VLOOKUP function
}