How to turn a range value to a double (VBA)

Question

So I want to make a function that takes a value in a cell to make some calculations, but whenever I try to get the value from the cell rather than hard-code it I get a #VALUE! error whenever the function is run. Whereas this did not happen when the value is hard-coded.

I believe that this is because the Range.Value returns a Variant, but I don't know how to turn the data to a double so that the function works right.

Function IfMissionarySupplies(Missionary_Type As String) As Double
Wb = ThisWorkbook 'Wb is a global variable.
Dim Elder_Supplies, Sister_Supplies As Double
Elder_Supplies = Workbooks(Wb).Worksheets("Control Variables").Range("C11").Value
Sister_Supplies = Workbooks(Wb).Worksheets("Control Variables").Range("C14").Value
If Missionary_Type = "Sisters" Then
    IfMissionarySupplies = Sister_Supplies
    Exit Function
ElseIf Missionary_Type = "Elders" Then
    IfMissionarySupplies = Elder_Supplies
End If 
End Function

I've searched over and over in the internet, but to no avail. I am also new to VBA so I might be overlooking something obvious to more experienced VBA developers.

Thanks!

Answer 1

I put the following in a standard module:

Function IfMissionarySupplies(Missionary_Type As String) As Double
    Wb = ThisWorkbook.Name 'Wb is a global variable.
    Dim Elder_Supplies, Sister_Supplies As Double

    Elder_Supplies = Workbooks(Wb).Worksheets("Control Variables").Range("C11").Value
    Sister_Supplies = Workbooks(Wb).Worksheets("Control Variables").Range("C14").Value

    If Missionary_Type = "Sisters" Then
        IfMissionarySupplies = Sister_Supplies
        Exit Function
    ElseIf Missionary_Type = "Elders" Then
        IfMissionarySupplies = Elder_Supplies
    End If
End Function

and setup the worksheet as follows:

So the above version of your UDF does appear to work!