How can I use enum identifiers in Excel UDF

I've created a function called EnergyPrice with the following code:

Here's the pricetable I'm looking up from

Prijstabel                  
                               fixed           variable 
Startdate   Einddate  开发者_如何学Go  gas       electra   gas      electra
                        €/a       €/a       ct/KWh   ct/KWh

1-1-2010    1-7-2010    181,00    235,00     0,11      0,33 
1-7-2010    1-1-2011    362,00    470,00     0,33      1,30 
1-1-2011    1-7-2011    191,00    245,00     0,22      0,65 
1-7-2011    1-1-2012    162,35    208,25     0,19      0,55 
1-1-2012    1-7-2012    324,70    416,50     0,37      1,11 

And here's the relevant code

Public Enum Energietype
  v_gas = 1
  v_electricity = 2
End Enum

Public Enum FixedOrVariable
  v_fixed = 1
  v_variable = 2
End Enum

Public Function EnergyPrice(PriceDate As Date, E_type As Energietype, variabel As FixedOrVariable) As Variant

Dim PrijsTable As Range
Dim RowNr As Integer
Dim Found As Boolean
Dim KolomNr As Integer

  Set PrijsTable = Range("EnergyPriceTable")
  If PrijsTable.Columns.Count <> 6 Then Err.Raise Number:=vbObjectError + 1000, Description:="No valid valid pricetable defined"
  RowNr = 1
  Found = False

  While Not (Found) And (RowNr <= PriceTable.Rows.Count)
    Found = (PriceTable.Cells(RowNr, 1).Value <= PriceDate) And (PriceTable.Cells(RowNr, 2) > PriceDate)
    If Not (Found) Then RowNr = RowNr + 1
  Wend
  If Found Then
    If E_type = v_gas Then KolomNr = 1
    If E_type = v_elektra Then KolomNr = 2
    If variabel = v_variabel Then KolomNr = KolomNr * 2
    KolomNr = KolomNr + 2
    EnergyPrice = PriceTable.Cells(RowNr, KolomNr).Value
  Else
    EnergyPrice = Empty
  End If
End Function

The question is how do I use the above enums in an Excel spreadsheet? So I can enter a formula like:

If I use the numbers 1,2 the functions works fine, but I want to use the enum names.

Can this be done using only Excel VBA?

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If you add the enums to the workbook as defined names, you can pass them into functions and the value that is passed is the actual value you set the enum for. Do this manually or via VBA if you prefer.

Example:

ActiveWorkbook.Names.Add Name:="v_gas", RefersToR1C1:="=1"
ActiveWorkbook.Names.Add Name:="v_fixed", RefersToR1C1:="=2"

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The only way I see, is by defining Names in your workbook, assigning them the constants of your Enums.

• From the menu: Insert ... Name .... Define
• Name: v_gas
• Refers to: =1

Alternatively, you could create those names by VBA, but that has no interest, since it will be a 1 shot (names are saved with the workbook).

By using such names, the users will be able to use F3 while entering the formula.