Vba instead of nested if

Hello,
I'm trying to create an excel sheet, to calculate the bill of material of windows and doors. In the attachment you can see a sample of the table. My problem is, that i have to create a very long nested if, to calculate the necessary amount of wood.
I thought to arrange the table to use lookup, but i didn't succeed.
I'm opened to other suggestion,but i think i have to use vba.
Right now, the only working nested if is for windows with one opening.
I'm looking for materials, to begin to build the vba code.


For the mods: i hope i didn't open this thread, in the wrong section,if so, you can move it.