[Typo3] IFRAME - how to make src the current page?

[Nige]

Hi all,

I am building a site where I will have a window containing the content 
in the centre of the screen.

Obviously, if the content is longer than the window, the window will 
grow to allow the content to fit (it's made using table & div elements).

What I want is the window to stay a fixed size and scrollbars to appear 
where the content is too long...so I thought I'd use an IFRAME.

The line of typoscript currently is...

page.wrap = <table class="tablemainpage"><tr><td class="tdmainpage"><div 
class="divmainpage">|</div></td></tr></table>

I want to add the IFRAME around the <div> tags like this...

page.wrap = <table class="tablemainpage"><tr><td 
class="tdmainpage"><IFRAME src=???? height=600 width=800><div 
class="divmainpage">|</div></IFRAME></td></tr></table>

My problem is how do I refer the src= statement in the IFRAME tag to the 
current page?

Cheers

Nige