fade in and fade out a stack panel when button is clicked in silverlight 4.0

I am having a stack panel and Two arrows pointing Up and down let may say.

when i clicked in the down arrow, the stack panel should fade out (i.e), the stack panel should show and the down arrow should changed to Up arrow.

when the up arraw is clicked, the stack panel should fade in (ii,e) it should be hind and the up arraw should change to the down arraw.

I hope my logic is cleat to u all.

Please bring me with the solution or link ASAP.

Thanks.