I am a beginer with cakes and have pretty much only made them from scratch. I would like to experiment with different cake flavors and suped up box mixes. That way I can make more variety! I have somebody that presented me with the challenge of a cheesecake flavored cake with strawberry filling. I know I read on here how to flavor a cake mix with a cheesecake pudding mix but can't seem to find it now! Anybody have instructions for that? Also I have only used buttercream and cream cheese fillings..what is the best way to fill it with strawberry and does it then need to be refrigerated? Thanks!

A good place to start would be the Cake Mix Doctor cookbook. It has lots of recipies for tweaking box cakes.

You can also google "doctored cake recipes" and find lots of great recipes. As far as using the pudding just add it to the mix.
My fav doctored is Betty Crocker mix add
an extra egg,
a box of instant pudding (flavor depends on cake flavor)
a cup of sour cream and a
little less water than the box calls for.
Sliced fresh strawberries on top of the creamcheese frosting or creamcheese pudding (whatever you use for filling.)
and yes I would refrigerate.hth

Here's a recipe for a cream cheesy cake:
1 box duncan hines cake mix white
4 egg whites
1/2 c. water
1/3 c. veg oil
1 sm. box INSTANT pudding in cream cheese flavor
1 cup sour cream

Mix for 2 mins after combined. Batter will be thick. Bake at 350. 30-35 mins.

Also, Willton's site has a great and delishious recipe for fresh strawberry filling but I think it has to be refrigerated.

Or you could just use strawberry jam. Hope this helps.