How to get cell value in Google Sheets using apps script. See article here: http://blog.gsmart.in/google-sheet-script-get-cell-value/ ‎

get-cell-value.js

function onOpen() 
{
  var ui = SpreadsheetApp.getUi();
  ui.createMenu('GetValues')
      .addItem('get current', 'getCurrentCellValue')
      .addItem('get by row col', 'getByRowAndColumn')
      .addItem('get by address a1', 'getByCellAddressA1Notation')
      .addToUi();
}

function getCurrentCellValue()
{
  var cell = SpreadsheetApp.getActiveSheet().getActiveCell();
  var a1 = cell.getA1Notation();
  var val = cell.getValue();
  
  SpreadsheetApp.getUi().alert("The active cell "+a1+" value is "+val);
}

function getByRowAndColumn()
{
  var ui = SpreadsheetApp.getUi();
  
  var response = ui.prompt(
      'Cell address',
    'Please enter the cell address in this format: row,col for example, 5,2 means row 5 col 2',
      ui.ButtonSet.OK);
  
  var resp_text = response.getResponseText();
  
  var match = resp_text.match(/^(\d+)\,(\d+)/);
  
  
  var row = parseInt(match[1]);
  var col = parseInt(match[2]);
  var value = SpreadsheetApp.getActiveSheet().getRange(row,col).getValue();

  
  SpreadsheetApp.getUi().alert("The value is "+value);
}

function getByCellAddressA1Notation()
{
  var ui = SpreadsheetApp.getUi();
  
  var response = ui.prompt(
      'Cell address',
      'Please enter the cell address (A1 notation)',
      ui.ButtonSet.OK);
  
  var a1 = response.getResponseText();
  
  var value = SpreadsheetApp.getActiveSheet().getRange(a1).getValue();
  
  ui.alert("cell value "+value);
}