[JS CS3, Win] Saving InDesign using app.activeDocument.save

Question

Hello.
I am having problems saving an InDesign document using Javascript.
My aim is to have a box in the document where I will type the filename and path where I want the InDesign file to be saved (eventually this will be generated from a datamerge).
I then want to run a script which will read the contents of the box and then save the document to that filename or location.
At the moment I have:
//SaveText.jsx
//An InDesign CS3 JavaScript
//Saves the document to the provided path
//get contents of the FileNameBox box on the document
var varFileName = app.activeDocument.textFrames.item("FileNameBox").contents;
//now save
app.activeDocument.save("/"+ varFileName+".indd");
//alert (app.activeDocument.filePath);
When I run the script (with "Hello" in the FileNameBox) the file changes name on the top bar of InDesign to "Hello.indd", but (when I run the commented out alert at the end) the file is not actually saving anywhere.
If I close InDesign and then open it the file is listed under "Open Recent" on the menu, but clicking it does nothing - again the file doesn't exist.
Does anyone have any ideas to help me from tearing my hair out?
Where is my file saving? (Or, if it isn't, how can I make it save!).
Thanks in advance for any help you can offer.

Answer 1

var myFolder = new Folder("~/Desktop/Test");
if (!myFolder.exist) myFolder.create();
var varFileName = app.activeDocument.textFrames.item("FileNameBox").contents;
app.activeDocument.save(myFolder.fsName + "\\" + varFileName+".indd");
alert(app.activeDocument.filePath);