I have a spreadsheet that contains sales values for each month. As there can be more than one value for a month I am using the subtotal function to aggregate the sales to give me twelve values (one for each month). The spreadsheet is maintained on an ongoing basis, so new entries are added from time to time. The data range also has an auto filter so that I can select the records for any particular month if needed.

Currently, February only has one record. After applying the subtotal function to the range, I have added a second record for February, but the subtotal does not update. I am adding the second record by inserting a row and entering the values. However, the subtotal does not update itself irrespective of whether I add the row before or after the existing record.

If a month contains more than one record to begin with, I can insert a third row in between the two existing records and the subtotal will update automatically. The problem is specific to only having one record when the subtotal is set up in the first instance.

Example:

Month Sales($)
Jan 100
Jan 150
Jan 100
Jan Total 350
Feb 250
Feb Total 250
Mar 120
Mar 140
Mar Total 260

In the above example, The Feb Subtotal will not automatically update no matter where I insert a second record for Feb.

Help!