Zoom in-out Every X sec

Hello,

i'm new at video editing and i need help.

I have a video for ex. 30min and i want to zoom in and back to normal every 20sec for 1sec zoom

how can i do it ?
i use sony vegas

I realize that not everyone wants to pay for Adobe, but After Effects scripting/expressions would be a perfect tool for this. With a few quick Google searches and some experimentation you can automate this task very easily.