What is the best way to check if the file exists, is not open, and is a CSV file?

First, I will show my code that I currently have:

Public Function IsThisCSV(sFile As String) As Boolean Dim ff As Long Dim fLine As String Dim sLineSrc As Variant Dim sLineRpt() As String Dim i As Long sLineSrc = Array("Interval Start", "Interval End", "Interval Complete", "Filters", "Agent Id", "Agent Name", "Release Date/Time", "Score", "Critical Score", "Average Score", "Average Critical Score", "Highest Score", "Highest Critical Score", "Lowest Score", "Lowest Critical Score", "Evaluation Form Name", "Evaluator", "Assignee", "Reviewed By Agent", "Interaction Date/Time", "Evaluation Date/Time", "Media Type", "Agent Comments", "Status", "Disputes", "Revisions") If Not DoesFileExist(sFile) Then IsThisCSV = False Exit Function End If If IsFileOpen(sFile) Then ' File is locked, cannot read it IsThisCSV = False Exit Function End If If FileLen(sFile) = 0 Then IsThisCSV = False Exit Function End If ff = FreeFile Open sFile For Input As #ff If Not EOF(ff) Then Line Input #ff, fLine End If Close #ff fLine = fLine = Replace(fLine, """", "") sLineRpt = Split(fLine, ",") If UBound(sLineSrc) <> UBound(sLineRpt) Then IsThisCSV = False Exit Function End If For i = LBound(sLineSrc) To UBound(sLineSrc) If UCase(Trim(sLineRpt(i))) <> UCase(Trim(sLineSrc(i))) Then IsThisCSV = False Exit Function End If Next i 'If we reach here, it's valid IsThisCSV = True End Function Public Function IsValidWB(sFile As String) As Boolean Dim wb As Workbook Dim xlApp As New Excel.Application xlApp.Visible = False SetAppSettings False, xlApp If Not DoesFileExist(sFile) Then IsValidWB = False GoTo Cleanup End If If IsFileOpen(sFile) Then ' File is locked, cannot open it for this check IsValidWB = False GoTo Cleanup End If If FileLen(sFile) = 0 Then IsValidWB = False GoTo Cleanup End If On Error Resume Next Set wb = xlApp.Workbooks.Open(FileName:=sFile, ReadOnly:=True) On Error GoTo 0 If Err.Number <> 0 Then ' An error occurred, so it is likely not a valid or non-corrupt workbook IsValidWB = False Err.Clear ' Clear the error Else ' No error occurred, so it is a valid workbook IsValidWB = True ' Close the workbook without saving changes wb.Close SaveChanges:=False End If Cleanup: Set wb = Nothing SetAppSettings True, xlApp If Not xlApp Is Nothing Then xlApp.Quit Set xlApp = Nothing End Function Public Function DoesFileExist(sFile As String) As Boolean Dim FSO As Object Set FSO = CreateObject("Scripting.FileSystemObject") On Error Resume Next DoesFileExist = FSO.FileExists(sFile) On Error GoTo 0 Set FSO = Nothing End Function Public Function IsFileOpen(sFile As String) As Boolean Dim fileNum As Integer Dim errNum As Long On Error Resume Next fileNum = FreeFile() Open sFile For Input Lock Read Write As #fileNum errNum = Err.Number On Error GoTo 0 If errNum = 0 Then Close #fileNum IsFileOpen = (errNum <> 0) End Function 

So, to further explain: Sheet1 = Start Here, on this sheet, there are 3 files that need to be loaded. The user will click on a button to select that file.
File1 = This is a file downloaded from Sharepoint, it's a CSV file. File2 = This is a daily file emailed from our Call Center Application. It only contains the updated information. File3 = This is the report file, it'll by manually created to start it, but file1 and file2 are used for data.

Right now, I am trying to make sure that file1 and file2 are good using the above Subs/Functions. I included the SetFile as that is how the user selects the file.

I've been using the Google AI from google.com and it keeps saying I should change this, I make the change, and recheck, it says I need to change that. So I change that, recheck, and it says I have to change this again.

So I am checking with the experts here. If more questions are needed, please ask. Any changes to make it more robust and more generic would be helpful.

Edit 1:

So, I think this now catches everything. I modified the above code to what I have now.