How can I zoom Keyframing ?

Please.. how can I manage a zoom in or zoom out of a clip by using keyframes??

is it any way to do this?? or is this a missing feature yet?

sometimes the way to play with keyframes applying effects and compositing is not quite clear and tends to get a bit messy or confusing.. perhaps is cause I keep thinking on the intuitive way Premiere and AfterEffects have set already a standard quite easy to understand ...

anyway .. I still think this program is one of the best in the open source arena.. with lots of future really !!

thanks a lot !!