photoshop cs2 question...

what are the buttons that I push when in the lasso tool to add or subtract from what I already have selected.. I know I hold down "Alt" to subtract. i Just cant figure out what to push if I missed something and want to add it to my selection.. any help would be great!
Thanks

I think it's shift. 'coarse I'm more used to the Mac controls because that's what we're using at school.

it is shift.. THANKS for the help!!!