[TYPO3] How can I set my extension parameters dynamically?

[PEF]

Hey,
I'm about to write an extension - my first - that can contain a flash 
movie. One of my setup variables is flashVars and I want to be able to 
set the parameter dynamically i.e.:

..
plugin.tx_bdflashcontainer_pi1.flashVars = uid={global:id}
..

... and there by be able to control the flash depending on the page id.

flashVars is defined in ext_typoscript_setup.txt:
flashVars=

The above example won't work - flashVars is set to TEXT instead of 
uid=15 or whatever the actual id is.

Of course if I write:

plugin.tx_bdflashcontainer_pi1.flashVars = uid=15

.. flashVars is set correct ... but not dynamic.

I've tried to define flashVars as:
flashVars = TEXT
flashVars.value =

... but without any luck.

Does anyone know how to handle this problem?

Regards
Peter Falk