UDF - How to turn a string that contains a path, workbook name, worksheet name and cell reference into a formula? [duplicate]

Answer 1

You can't use a UDF to insert a formula. I'm afraid you'll have to use an XLM macro to reference a range in a closed file. I found this information HERE

So in practice:

My testfile value:

The somewhat edited code:

Private Function GetValue(path, file, sheet, ref)

Dim arg As String
If Right(path, 1) <> "\" Then path = path & "\"
If Dir(path & file) = "" Then
    GetValue = "File Not Found"
    Exit Function
End If
arg = "'" & path & "[" & file & "]" & sheet & "'!" & Range(ref).Range("A1").Address(, , xlR1C1)
GetValue = ExecuteExcel4Macro(arg)

End Function

Sub TestGetValue()

With ActiveWorkbook.Sheets(1)
    path = .Cells(1, 3)
    file = .Cells(2, 3)
    sheet = .Cells(3, 3)
    ref = .Cells(4, 3)
    .Cells(1, 1) = GetValue(path, file, sheet, ref)
End With

End Sub

Use a button and assign macro to run on click

Answer 2

Based on what I found here it is possible to change cells with an UDF and insert a formula.

It is a little bit cumbersome (maybe there is someone out there who can improve it) but it works. You also need to do a recalculation what you can't trigger from the function getValue and the sub addFormula. You must put it somewhere else. The parameter rg is the cell where you want to put the formula. Make sure is is not the cell where you put getValue.

Function getValue(rg As Range, path As String, file As String, sheet As String, ref As String)
    Evaluate "addFormula( " & Chr(34) & rg.Address & Chr(34) & "," & Chr(34) & "'" & path & "[" & file & "]" & sheet & "'!" & ref & Chr(34) & ")"
    getValue = ""
End Function

Sub addFormula(trgAddress As String, myFormula As String)
    Dim trgRg As Range

    Set trgRg = Range(trgAddress)
    trgRg.Formula = "=" & myFormula

End Sub

In the worksheet selection change I added the calculate method. This is for sure not the best way to do it but it shows it is possible.

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    Me.Calculate
End Sub

And that how you can use it: The function is in D5, the result in E5