Firstly, hi all! I'm new here and I hope you guys can help me and, in the future, I can help others...

So here's the deal:
I'm doing this table in which I put some information about rooms in a construction job, including: room areas, perimeter, height, wall areas, and windows/doors dimensions.

To calculate wall area, I need to multiply the perimeter and the room height, and then subtract the windows/doors areas the room has. So I made this cell that lists the doors and windows the room has, in the following format: "W1,W1,W3,D1" (2 windows of type 1, one window of type 3 and a door of type 1).
I need to know if it's possible to make Excel read this cell and automatically recognize the cells with those names, read their contents, and subtract them...

To make it simpler to understand:

Cell1: Perimeter
Cell2: Height
Cell3: Wall Area -> =(Cell1*Cell2)-?????
Cell4: id's of the doors and windows -> W1,W1,W3,D1
Cell5: Area of W1
Cell6: Area of W3
Cell7: Area of D1

So I need that Cell4 displays the area of the wall - the area of doors and windows, but since those can change a lot in the project, I'd rather make it rational, and not need to update every formula when I change something in the project that afects many rooms...
So if I change a W1 for a W2, I need it to automaticaly detects that W2 has another area and use it in the formula to get the actual area of walls.

I'm thinking I should somehow be able to give Cell5 the "name" of "W1" and then make Cell4 "forward" the content of Cell5 to Cell3's formula.

Is that possible? Am I being confusing? Here is a screenshot of the table I'm working at (please apologize since it's in portuguese, my native language, but if it helps: Pé direito = Height, J1 = W1 and P1 = D1 and so on)

Image

Btw sorry I didn't search for an answer first, but I just don't know what term to seach for...