can i make a marble cake out of cake box? I cant find it in the super market. Could I use chocolate cake box mixed with the vanilla cake mix and marble it?

Yes you can. Are you doing more than one tier? I made a marble cake a few weeks ago using an enhanced recipe for a vanilla bean cake and a chocolate fudge marble, and weighed out half of each box so I wouldn't be wasting batter.

I just did one! I couldn't find a marble cake mix so I bought a chocolate cake mix and a vanilla cake mix and put them together. It was delicious!

I mixed a triple chocolate cake with a vanilla cake once, and I was not impressed with my results personally. I have since used Duncan Hines marble and liked that one better than my mixing two cake mixes! Marble IS a hard cake to find in the stores, which was why I mixed two cakes also... Good luck!