Thank you for your answer.
Okay, to get the data each week, we do need to aggreate the data in a pivot table - this would be not the big deal!
Your idea with query + page works as suspected, but this is only useful for one "keyword" at once.
But there seems no possibility to use this idea e.g. for 100 keywords at once, right? Or is there a way for this?
The background about this:
at the moment we do have a xovi account, but we use it more or less only for keyword monitoring....
...if it would be possible to get this info through the integrated google services, then we would not need to pay for the xovi account anymore