Ok I may have a solution for you but it will change a bit the structure of your page.
I would use the same technique I’m describing in my slider tutorial.
Basically it’s the same technique except the slides are vertical instead of horizontal.
The only other setting that would be different will be to set the overflow of the slider mask to scroll instead of hidden and you should have the desired result.
Let me know if you need extra help to set it up.
Here is the thread where you can find my tutorials 