Generate Random Number with conditions (watermark pdfs)

Requirements:

Watermark around 100 pdf file of around 100 pages each  with below conditions:

1.   5 Pages to be watermarked for each file excluding Pages 1 - 5

2.  All 5 pages for each file should be different .. ex- if File1  was watermarked on page nos. 11, 22, 49, 80, 95 then second file2 should be watermarked with different set of pages ex- page nos. 14, 18, 49, 90,99 and so.. on

3. Each file must close automatically without prompting to save dialog box everytime.

        I am using the below script to save file but still prompting the save dialog box

var oMyDoc = this.documentFileName;

app.execMenuItem("Save", oMyDoc);

this.closeDoc(true);

I have the following script for watermarking and generating random number:

var cMyText = util.printd("mm/dd/yyyy", new Date);

var r = Math.floor(Math.random() * 100) ;

if (r > 10){var first = r; }

this.addWatermarkFromText({

cText: cMyText,

nRotation: 45,

cFont: "Helvetica-Bold",

nFontSize:20,

aColor: color.gray,

nStart: this.pageNum=first

nOpacity:0.5});

Thanks in advance