Custom PyQt4 TableWidget

[ff]

I am creating a custom widget based on a PyQt QTableWidget and i want
to stop PyQt highlighting all the cells when the very top-left 'thing'
is clicked, (dont know what to call it, its the bit that sits on the
same row/column as the hozizontal/vertical header items), i cant find
a way to do this, any suggestions? even the signal that is emitted
when this 'thing' is clicked would be useful as i can manually un-
highlight them all, but i cant find that either!

any help appreciated,

ff