Excel summarizing with code - excel

Question

I am working in woodworking industry. I want to speed up my workflow using reusable worksheets in excel. I am making material quotation, summerazing all the stuff what we need to build the cabinets. These cabinets usually custom cabinets, I have to write all the sizes, quantities etc by my hand, after I done I must summarize the data to make a price offer. I did a script in Blender python, works fine, but I need to do it in Excel worksheets aswell. My problem:
I write down the sizes for a board (which has 4 sides).
No problem to get the square meters I just simply multiply the numbers. But I have a cell called "Edgebanding". We use two types of it: 1 is called PVC (small letters) 2 is called ABS (capital letters). To summarize these I need a code (I am coding like 8 years now). I just simply write down the code what I need:
SUMPVC = 0
for length of string(Edgebanding cell) with each letter
if currentLetter='a' then
SUMPVC+=BoardWidth(B Cell value)
elif currentLetter='b'
SUMPVC+=BoardHeight(D Cell value)
end for cycle
return width SUMPVC*Quantity(F cell value)
SUMABS = 0
for length of string(Edgebanding cell) with each letter
if currentLetter='A' then
SUMABS+=BoardWidth(B Cell value)
elif currentLetter='B'
SUMABS+=BoardHeight(D Cell value)
end for cycle
return width SUMABS*Quantity(F cell value)
Is it possible (and if so..how?) to make this as a function like the other operators in excel (like "=SUM(range)".
So it seems like "=SUMPVC(E2)" and "=SUMABS(E2)
I attach a screenshot, just to be clear what I am talking about.
Thanks in advance! Alex
Example

Answer 1

I do not have 50+ reputation, so I cannot post this as a comment:
In the link above, there is a small tutorial on how to create a formula. Just adapt to your need.
http://www.dummies.com/software/microsoft-office/excel/how-to-create-custom-excel-functions/