I think we need a little more information about your process -

You say you're saving the bank statement to a file in .xls format.  Then
when you open that file later, that data should still be there.  

I'm actually thinking that you may be well served with a simple manual
process:
get your latest statement information into an Excel workbook,
open your 'permanent' record workbook, then copy from the latest information
and use Paste Special with the [Values] option chosen to paste the latest
information at the end of previous information in the 'permanent' workbook.