Imagache force Image creation

Hello,

I'm a newbie in Drupal.
I am using the Imagecache Module in combintaion with the Services Module.

The Problem is, that Imagecache produce the Images only on a request.
So a have a Problem with Services.
The Imagecache Module has to create the Image directly after the User
uploaded the Image (respectively after it is submitted by the form).

I have found this.
http://happypixels.net/blog/triggering-creation-imagecache-derivatives-programmatically, but i don't know where I have to paste it.
I would like to have the Code in the Imagecache Module, so don't need to call the function.

What function in Imagecache is called after the form is submitted, so i can paste the code below?

Thanks