Object invoke error ... sometimes

[pgag45]

Public Function openIndexFile(sheetName As String) As Boolean
DoEvents
Dim wb1 As Workbook
Dim wb2 As Workbook
Dim sh As Object
 
Dim sfilename As String
Dim temp As String
Dim shtnext As Variant
Dim found As Boolean
 
Set wb1 = ThisWorkbook
 
For Each shtnext In Sheets
    If shtnext.name = sheetName Then
        Sheets(sheetName).Visible = True
        Application.DisplayAlerts = False
        Sheets(sheetName).Delete
        Exit For
    End If
Next shtnext
    
sfilename = Application.GetOpenFilename(filefilter:="Excel Files (*.xls), *.xls", Title:="N-INDEX")
If sfilename = "False" Then Exit Function
 
Set wb2 = Workbooks.Open(FileName:=sfilename)
 
On Error Resume Next
Set sh = wb2.Sheets(sheetName)
On Error GoTo 0
If sh Is Nothing Then
    wb2.Close SaveChanges:=False
    MsgBox ("No " & sheetName & " was found in that file.")
    openIndexFile = False
    Exit Function
End If
 
 
On Error Resume Next
Application.DisplayAlerts = False
wb1.Sheets(sheetName).Delete
On Error GoTo 0
 
sh.Copy After:=wb1.Sheets(wb1.Sheets.count)
wb2.Close False
Set wb2 = Nothing
 
wb1.Sheets(sheetName).Visible = xlVeryHidden
wb1.Sheets("Driver").Activate
Application.DisplayAlerts = True
openIndexFile = True
Set wb1 = Nothing
Set sh = Nothing
End Function