Sub demo()
 
    Const strNEW_NAME As String = "File 1"
 
    'a workbook cannot have sheets with duplicate names
    If Not SheetExists(ThisWorkbook, strNEW_NAME) Then
        'sheet1 is the codename of the sheet, determined at design time
        Sheet1.Name = strNEW_NAME
    End If
 
End Sub
 
'a generic function to check if a sheet exists
Private Function SheetExists(ByVal wkbTarget As Workbook, ByRef strName As String)
    On Error Resume Next
    SheetExists = Not wkbTarget.Sheets(strName) Is Nothing
End Function