Writing function with multiple (13) if/and/then statements

Hello,

I am currently trying to write a function with multiple if/and/then statements and realized after about 2 that I would be here all day if I continued this way. For example, If I want to calculate the surface area of a building face and remove the area of the windows, but there are 6 windows and I want to calculate surface area every inch up the face of the building. So, the first criteria would be the surface area of the face up to the bottom of the first window is just the surface area of the wall (i.e. If(A4<C2,B2*B3)). But as soon as the height reaches the bottom of the first window, the SA calculation would change to subtract out the surface area of the window to that point. I have attached a skeleton spreadsheet, please let me know if there is a faster way to go about this than 13 criteria if statements.


Thanks in advance.