You could try to rename the first worksheet in the workbook using code like:
Option Explicit
Sub auto_open()
Dim myNewName As String
myNewName = ThisWorkbook.Name
If LCase(Right(myNewName, 4)) = ".xls" Then
myNewName = Left(myNewName, Len(myNewName) - 4)
End If
On Error Resume Next
Worksheets(1).Name = myNewName
If Err.Number <> 0 Then
MsgBox "Worksheet was not renamed!"
Err.Clear
End If
End Sub
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm