I'll throw this out there and then duck.
The usual reason to check if a file exists is to avoid an error when attempting to open it. How about using the error handler to deal with that:
Function openFileTest(filePathName As String, ByRef wkBook As Workbook, _
errorHandlingMethod As Long) As Boolean
'Returns True if filePathName is successfully opened,
' False otherwise.
Dim errorNum As Long
'***************************************************************************
' Open the file or determine that it doesn't exist.
On Error Resume Next:
Set wkBook = Workbooks.Open(fileName:=filePathName)
If Err.Number <> 0 Then
errorNum = Err.Number
'Error while attempting to open the file. Maybe it doesn't exist?
If Err.Number = 1004 Then
'***************************************************************************
'File doesn't exist.
'Better clear the error and point to the error handler before moving on.
Err.Clear
On Error GoTo OPENFILETEST_FAIL:
'[Clever code here to cope with non-existant file]
'...
'If the problem could not be resolved, invoke the error handler.
Err.Raise errorNum
Else
'No idea what the error is, but it's not due to a non-existant file
'Invoke the error handler.
Err.Clear
On Error GoTo OPENFILETEST_FAIL:
Err.Raise errorNum
End If
End If
'Either the file was successfully opened or the problem was resolved.
openFileTest = True
Exit Function
OPENFILETEST_FAIL:
errorNum = Err.Number
'Presumabley the problem is not a non-existant file, so it's
'some other error. Not sure what this would be, so...
If errorHandlingMethod < 2 Then
'The easy out is to clear the error, reset to the default error handler,
'and raise the error number again.
'This will immediately cause the code to terminate with VBA's standard
'run time error Message box:
errorNum = Err.Number
Err.Clear
On Error GoTo 0
Err.Raise errorNum
Exit Function
ElseIf errorHandlingMethod = 2 Then
'Easier debugging, generate a more informative message box, then terminate:
MsgBox "" _
& "Error while opening workbook." _
& "PathName: " & filePathName & vbCrLf _
& "Error " & errorNum & ": " & Err.Description & vbCrLf _
, vbExclamation _
, "Failure in function OpenFile(), IO Module"
End
Else
'The calling function is ok with a false result. That is the point
'of returning a boolean, after all.
openFileTest = False
Exit Function
End If
End Function 'openFileTest()