Masking in Axure

Hi,
I am trying to build an interaction that by clicking on a target another element appear inside that with sliding animation, my problem is this element is outside of the target area and hidden, when I show it, it appears from outside the target area.
I want this element to appear from inside target, like masking outside area.
How can I do this in Axure?
here is axure file
mask.rp (66.4 KB)

You can mask by placing your content in a Dynamic Panel with a fixed size. When you edit a state of such a panel you’ll see a blue dotted line that represents the size of the panel. Anything beyond the dimensions of the panel will be hidden.

To make it fixed sized, right click the panel and make sure Fit to Content is unchecked.

Thanks,
Have you checked my file?
I tried to make it dynamic panel but still it shows the element coming inside from out of dynamic panel.
Which item should be a dynamic panel?

Can’t check your file currently but everything that should be masked should be in the panel.