How to calculate 2-D wavelet energy?

Hi, I want to ask how to calculate the energy of 2-D wavelet decomposition. I know that function wenergy2 can be use, but I want to know how it can be calculated since I want to use single level 'dwt2' function and decompose the images level-by-level instead of using this; [C,S] = wavedec2(X,2,'bior3.7'). (I have my own reason why I need to decompose it like that)

If 'dwt2' is used, I can't calculate the energy using 'wenergy2' since I didn't know how to get the 'C' array.

Please help me, give me some ideas how to solve this.