fo:block-container question

Hi,
I am trying to use fo:block-container.
I have XML documents which are laid out in either
single-column format or two-column format.
Irrespective of what format the document is I would
like to have some specific information in a block
which I would like to place somewhere on the page. In
short I want to specify absolute position for the
fo:block-container I will be using. I am using FOP to
generate PDF's. 
What attributes should I specify for positioning the
block in this way. I tried but the results are not
what I expect. The problem is that this
block-container is placed over some content i.e. the
content is hidden behind this container. What I want
is that the remaining content should flow into the
areas outside the container. I saw a property called
intrusion-displace. It takes values auto,none, inline
and some more. I tried using it but in Epic it gave me
an error saying 

"Property "intrusion-displace" in namespace
"http://www.w3.org/1999/XSL/Format"
is not defined."

I tried to use the stylesheet with FOP but the same
thing happens. FOP gives an error for the same but
doesn't tell why the error occurred. Is FOP compliant
with this property? 
Is there any other way to solve my problem. 
Thanks for the help.
Regards,
Abhi

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