I am trying to create an excel file from an user event script

var newAttachment = nlapiCreateFile('filename.xls', 'EXCEL', nlapiEncrypt("Test", 'base64'));
     newAttachment.setFolder(216);
     nlapiSubmitFile(newAttachment);

My question is, right now "Test" is going in the A1 in my excel file. How would I be able to put info in B1 or A2? I.E The next row or column? Thanks!