function onOpen() {
  var folder = DocsList.getFolder("My folder");
  var contents = folder.getFiles();
  var file;
  var data;

  var sheet = SpreadsheetApp.getActiveSheet();
  sheet.clearContents();
  sheet.appendRow(["link to sheet", "Name", "Type", "Primary Contact"]);
  for (var i = 0; i < contents.length; i++) {
    file = contents[i];
    var value1,value2,value3;
    if (file.getFileType() === "SPREADSHEET") {
      var sheet = SpreadsheetApp.openById(file.getId()).getSheetByName("Site Demographics");
      var value1 = sheet.getRange('B7').getValue();
      var value2 = sheet.getRange('C7').getValue();
      var value3 = sheet.getRange('H9').getValue();
    } else {
      value1 = null; value2 = null; value3 = null;
    }
    data = [ file.getUrl(),value1,value2,value3]
    sheet.appendRow(data);
  }
};