I need to produce a 'report' from a whole bunch of different criteria used to generate the resulting document on the web.
This will need to be printed to an A4 sheet, but here is the rub - I need to be able to control page breaks. I need to show certain things on page 1, then a new page 2 and so on.

Is this possible??

Big problem is that I don't know where I need the pagebreak - its dynamically generated content from a number of options, which results in the finished document.

Its one of those things that is so close to working, but I cannot use it as the resulting report looks shit - and it's a report that clients see and also product providers, so it has to look decent.

Can someone show me the way on using Javascript to perform the A4 size calculation?

This is an "issue" I've visited many times. Unfortunately, formatting HTML to be viewed in a web page that will print exactly the way you want is near impossible---you aren't allowed that kind of control over the formatting with HTML.

With CSS, you can insert page breaks.
http://www.w3.org/TR/REC-CSS2/page.html

The other problem people have is how to know when to insert the page-breaks. For example, if I have 500 rows of data to print in a report, and I want a header and footer on all pages, and I want each page to nicely fit an 8.5 x 11 page, how many records can I print on each page? Good question! All you can do is set the font-size and line-height, etc using CSS, then make your best guess (trial and error) as to how many lines fit per page. If you have to deal with lines possibly wrapping---ouch--your job is that much more difficult.

If you REALLY need the report to look professional, and exact formatting is required, then this is what PDF's are designed for. You can programattically generate PDF's on the fly and serve to your customers on your website. Moderator Tgreer (www.tgreer.com) on this forum is one of the leading Postscript / PDF experts in the country and can provide further assistance. Maybe he will chime in on this thread.