How to allow for panel movement with a varnish finish

Hi all, I'm making a drinks trolley which is basically four legs with an upper and lower frame, each containing a panel/shelf.



The panels are made of solid timber so I have cut a rebate inside the frames to allow for movement in the manner of a raised panel door.



I normally use an oil finish, so I oil the panel before assembly, to avoid un-oiled edges being exposed when timber panel contracts, then oil the rest of the piece after assembly.



This time I am using a filming finish, like varnish, and I am worried if I do things as above, the panel won't be able to move freely in the rebate after I varnish, as it will be sealed in place by the varnish.



So what is the go in this situation?



Thanks in advance,

Peter