Specifying page range

Ok trying to merge some templates and scripts I have to one export an .indd file would like different options per page(s).

Here's what I currently have, that I would like to change to specify pages 1-13:

var myPageName, myFilePath, myFile;

var myDocument = app.documents.item(0);

var myBaseName = myDocument.name;

for(var myCounter = 0; myCounter < myDocument.pages.length; myCounter++){

myPageName = myDocument.pages.item(myCounter).name;

app.pdfExportPreferences.pageRange = myPageName;

and also have export as:

myFilePath = dirPath + docType + "/" + fileName;

myFile = new File(myFilePath);

myDocument.exportFile(ExportFormat.pdfType, myFile, false);

Here's is another script, that I would like to change to specify pages 14-17:

var myPageName, myFilePath, myFile;

var myDocument = app.documents.item(0);

var myBaseName = myDocument.name;

for(var myCounter = 0; myCounter < myDocument.pages.length; myCounter++){

myPageName = myDocument.pages.item(myCounter).name;

app.jpegExportPreferences.jpegExportRange = ExportRangeOrAllPages.exportRange;

app.jpegExportPreferences.exportResolution = 96;

   app.jpegExportPreferences.pageString = myPageName; 

and also have export as:

myDocument.exportFile(ExportFormat.jpg, File(myFilePath), false);

So how can I specify some pages to export as .pdf and some others to export as .jpg with a dpi. of 96?

Thanks in advance,

Joe