How to autoresize a layout in a scrollarea ?

I create a main layout(vertical layout) in a scroll area! Then create another vertical layouts in main layout!
Next in a layout i create two sub vertical layout ! in sub layout i create a push button ! Button 1 is showed! Button 2 is hided!
I want if i click into Button 1 , button 2 is showed and button 1 is hided! My problem is : The button 2 is large and i want the main layout autoresize when i click into button 1! when i click button 1 button 2 is showed but main layout is not expand!
this is picture :
http://ne8.upanh.com/b3.s17.d2/ab0bf....aaa.700x0.jpg

Help me!