Simplify Multiple If Else Statements

I'm using one spreadsheet "Take Off", to pull data from a cell which dictates an objects shape, based on this shape I have a very large IF statement that pulls data from an adjacent cell where an objects dimensions are entered, the statement than proceeds to use these dimensions to calculate the weight of the object.

I've run into the problem with only 7 IF statements, I have gone online and tried to figure out how to avoid this since it is a common problem, but I can't figure out how to do it, most of the examples show very simple and basic formulas. I am unable to figure out how to translate this into my IF statement where I make reference to many cells as well as us differant formulas within the IF statement.

My latest solution was to breakdown the IF statements and try to my my own functions but I think I am too green to have done this properly. Any guidance would be greatly appreciated.

The following is the code I'm working with followed by how I tried to remedy the situation:

=If(Or(C21="BPLT",C21="L"),(((Get_Word(D21,"First")+Get_Word(D21,3))/1000)*(Get_Word(D21,"Last")/1000)*(E21/1000)*7850),If(And(C21="PL",L21<4),(Get_Word(D21,"First")/1000*Get_Word(D21,"Last")/1000*E21/1000*7850), If(Or(C21="BP",C21="PL",C21="BAR"),(Get_Word(D21,"First")/1000)*(Get_Word(D21,3)/1000)*(Get_Word(D21,"Last")/1000)*7850, If(And(C21="HSS",L21>4),(Get_Word(D21,"First

I tried to make my own functions:

aCalc: =If(Or( 'Take-Off'!C13="BPLT",'Take-Off'!C13="L"),(((Get_Word('Take-Off'!D13,"First")+Get_Word('Take-Off'!D13,3))/1000)*(Get_Word('Take-Off'!D13,"Last")/1000)*('Take-Off'!E13/1000)*7850),"")

bCalc:

=If(And( 'Take-Off'!C13="HSS",'Take-Off'!L13>4),(Get_Word('Take-Off'!D13,"First")*2+Get_Word('Take-Off'!D13,3)*2)/1000*Get_Word('Take-Off'!D13,"Last")/1000*'Take-Off'!E13/1000*7850,"")

and so on until hCalc, but when I put them together in a cell like this:
=aCalc()+bCalc()+cCalc()+dCalc()+eCalc()....
I get an error #REF.

I realize a problem might be that I'm referencing a specific cell within my formulas, and many examples online show cells referenced in the form =A$1$, is there a differant way for referencing a cell, because currently I rely on Excel to automatically do this by way of relative reference.

ADDED: Ok I scrapped making the functions because I'm not sure and I did some research on VBA so I tried this one:

Function Weight(Shape As String, Amount As Double, Dimension As String, Optional Length As Variant)
If (Shape = "BPLT" Or Shape = "L") Then
If (Amount > 5) Then
Weight = Get_Word(Dimension, "First") / 1000 + Get_Word(Dimension, 3) / 1000 + Get_Word(Dimension, 5) / 1000 * Get_Word(Dimension, "Last") * 7850
Else
Weight = Get_Word(Dimension, "First") / 1000 + Get_Word(Dimension, 3) / 1000 * Get_Word(Dimension, "Last") * 7850
End If

But when I try to put Weight(C6,D6,F6,E6) I run into the error "Sub or Function Not Defined"