triggering function from iframe

i remember there being a way to trigger a function on the parent page from a button/link in an iframe. does anyone know the syntax? or what section of w3schools i should look at?

well, since noone is gonna reply... i figured it out by MYSELF!
you can grab any object, id, name, anything from the main page via an iframe.
all you do is: on the iframe you have function that says: parent.document.getElementById('id').innerHTML ="****ing bull****";