[TYPO3] how can I access a variable set in insert plugin cobject?

[Andrew Davis]

hi i have what im suer is a dumb question, but having problem finding answer

I have a variable that indicates pid (startingpoint) for a plugin on a 
page, set thru the typo3 backend (insert plugin on a page, then set 
config there). How can i access that value within the plugin (php), to 
use with a query ?

thanks for your help
andrew