Saving PDF Form with Filename picked from the form fields

I want to save my PDF form with a filename which will be picked from one of the form fields. I don't want path to be prefixed.. that may choosed by the user in the traditional way.. i only want the filename to be automatically there in the SAVE As dialog box from one of the form fields.

I got some of script from internet but none of them work for me.

// get the value of the form field

var text1Value = this.getField("Text1").value;

// make a file name from the field value

var newFileName = text1Value + ".pdf";

// get the path where the file is currently located

var filePath = this.path.replace(this.documentFileName);

// create the new full path

var newFullFilePath = filePath + newFileName;

try {

this.saveAs(newFullFilePath); // Only this will not work from a button...

} catch (e) {

app.alert("Error! Could not save as: " + newFullFilePath);

}