Flag & Rule trigger-taxonomy

Hi,

I'm using the flag module for almost everything,
but I don't have much experience with php.
but I need an action in php or a rule intergration to do sometgin like this

ON event A node has been flagged, under "objavi"
-------
if
not - taxonomy term "trash"
("trash" is a forum container for bad topics)
do
change taxonomy term to "trash"

help me please with this :'|