Activating closed workbooks - excel

Question

I am using the function below to extract data from other workbooks.
Function GetValue(path, file, sheet, ref)
'Retrieves a value from a closed workbook
Dim myArg As String
'Make sure the file exists
If Right(path, 1) <> "\" Then path = path & "\"
If Dir(path & file) = "" Then
GetValue = "File Not Found"
Exit Function
End If
'Create the argument
myArg = "'" & path & "[" & file & "]" & sheet & "'!" & Range(ref).Range("A1").Address(, , xlR1C1)
'Execute an XLM macro
GetValue = ExecuteExcel4Macro(myArg)
End Function
I am calling this function like this:
Sub TestGetValue()
Dim p As String, f As String
Dim s As String, a As String
p = "C:\Users\schaudha\Desktop\FIT transition\test simulation results"
f = "all cancer rate.xml"
s = "CONTENTS"
a = "A1"
MsgBox GetValue(p, f, s, a)
End Sub
This function seems to work only when the workbook is active. I mean, if I open the Excel file that I need data from and then run my subroutine, it works, but if it is closed, it doesn't work. I would also like it work when the workbook is closed. I am guessing I need to activate the workbook somehow before I use ExecuteExcel4Macro(myArg). How do I do that? I plan on using this function to extract data from thousands to cells from about a hundred workbooks, so I want to make this code as efficient as possible.

Answer 1

I think what you're looking for is (modified from your code):
If Dir(path & file) = "" Then
GetValue = "File Not Found"
Exit Function
else
CurrBook = Workbooks.Open Path & File
End If
'''Code here
CurrBook.Close
This will open the file, if it's found, and you'll be able to extract the data from it. I hope this helps!

Answer 2

This works
Function GetValue(path, file, sheet, ref)
'Retrieves a value from a closed workbook
Dim myArg As String
Dim CurrBook As Workbook
'Make sure the file exists
If Right(path, 1) <> "\" Then path = path & "\"
If Dir(path & file) = "" Then
GetValue = "File Not Found"
Exit Function
End If
Application.Workbooks.Open (path & file)
'Create the argument
myArg = "'" & path & "[" & file & "]" & sheet & "'!" & Range(ref).Range("A1").Address(, , xlR1C1)
'Execute an XLM macro
GetValue = ExecuteExcel4Macro(myArg)
Application.Workbooks(file).Close (False)
End Function

Answer 3

If you're going to open the workbook you don't need ExecuteExcel4Macro at all:
Function GetValue(path, file, sheet, ref)
Dim CurrBook As Workbook
'Make sure the file exists
If Right(path, 1) <> "\" Then path = path & "\"
If Dir(path & file) = "" Then
GetValue = "File Not Found"
Exit Function
End If
Set CurrBook = Application.Workbooks.Open(path & file)
On Error Resume Next
GetValue = CurrBook.Sheets(sheet).Range(ref).Value
CurrBook.Close savechanges:=False
End Function