Hi Dimitris!
One idea would be to have the scrolling linked to a timeline. So as the user scrolled the "Scale (Height)" would start at "100%" (or whatever) and to go to a higher percentage e.g. 500% as the timeline progressed.
Have not had the time to try this yet myself - but this idea, or a slight variance should work I would think.
A thread about linking the timeline with scrolling.
Notes: In the "Metrics Inspector" panel:
• Make sure that the "Transform Origin 'Y Offset' " is set to "0" for the element.
• Even though You are scaling just the height it might be necessary to un-check the "Constrain ratio" in the "Scale" section.