User input requirements for String values - vba

Question

Alright, I am trying to create a user defined function that will accept one character input, and then return a String. Although I couldn't get the Char data type to work for VBA (not sure why?) I was able to get it working fine if I inputted the single character value as a String.
Currently, when the UDF is running within Excel, it will work as long as quotes are placed around the String input, as shown:
=tradeClass("o")
that will work and return the correct result. But what I really would like to do is be able to write the Excel function in this manner:
=tradeClass(o)
I wrote out code that will concatenate "" onto the ends of my user input:
Public Function tradeClass(class As String)
Dim result As String
Dim before As String
Dim after As String
before = """"
after = """"
class = before & class & after 'my attempt to concatenate " on either side of the class input
Select Case LCase(class)
Case "s"
result = "Sale"
Case "r"
result = "Redemption"
Case "i"
result = "Exchange In"
Case "o"
result = "Exchange Out"
Case "x"
result = "Ignore"
Case "k"
result = "Settle"
Case "m"
result = "Transfer"
Case "w"
result = "ML PR3 Redemption (No longer in use)"
Case Else
result = "Invalid Entry"
End Select
tradeClass = result
End Function
It returns a #VALUE! error in Excel, so I am starting to think that I will always have to enter quotation marks with my character. Is this the case?

Answer 1

I can't imagine what compelling reason you have to want to do this. If you were truly determined, there is a hack/workaround/kludge that will allow this to work.
I strongly advise you not to use this, but you asked a question to which I have an answer. So here goes:
When you pass an unquoted string of character(s) to a function in Excel, it assumes that it is a reference to another cell. This is obvious in a function call such as =tradeClass(A1). That function will pass the value of the cell A1 to the function tradeClass.
Excel also supports naming cells to make formulas easier to follow. For example, you could assign the name "StartYear" to cell A1. So instead of using =DATE(A1, 1, 1) you could use =DATE(StartYear, 1, 1) which will be easier to maintain.
Now, in your case, we can abuse this power and name a bunch of cells s, r, i, o, x, k, m, and w. In the cell named s we would enter the letter "s" as the cell's value and so on. So then when you call =tradeClass(o), Excel will look up the cell named o and get its value (which we set to "o") and pass the value "o" of the cell named o to your tradeClass function.
This is a dreadful abuse of the cell-naming capabilities of Excel and violates all sorts of good programming practice. But ask, and you shall receive.
DISCLAIMER: Please do not actually use this.
One final note: When, someday, someone comes along and changes the value of the cell named o to the letter "s", please refer to the above disclaimer.

Answer 2

Unfortunately, if you want this function to work on user input as specified, you're going to need to pass in with quotes. Try out a built-in Excel function, for example:
=LEN(String)
vs.
=LEN("String")
The second one gives you 6, while the first one gives you an error.
However, your code would work nicely if the trade classes you're after are in their own column, like this:
Public Function tradeClass(Str As Variant)
Str = CStr(Str) 'force the variant to a string
Select Case LCase(Str)
Case "s"
result = "Sale"
Case "r"
result = "Redemption"
Case "i"
result = "Exchange In"
Case "o"
result = "Exchange Out"
Case "x"
result = "Ignore"
Case "k"
result = "Settle"
Case "m"
result = "Transfer"
Case "w"
result = "ML PR3 Redemption (No longer in use)"
Case Else
result = "Invalid Entry"
End Select
tradeClass = result
End Function

Answer 3

I know it’s an old question but got the same error and found the reason and something like this worked for me: you shall use Public Function tradeclass(class) and then class = class.address. Hope this helps!