Copying forward a number
 

Every day I do a reconciliation where I have to copy the figure from the
previous day's rec (B35), then subtract a figure from today's rec (B9) and
add a figure from another cell also in today's rec (D9) to give me the new
figure in B35. There are a number of worksheets and I have to do it for
every worksheet. What formula could I use instead? My main confusion is
that the previous day's file is saved with the format
singaporeyymmdd.yyyymmddand then 6 digits. The first dd is the previous day