Excel Problems

I am using a very simple spreadsheet adding columns of numbers into a SUM. It had been working just fine but now when I make a change to one of the numbers in the column, the change is not reflected in my sum/total cell.

At the end of the sheet I am adding several SUM/total cells to get one big total -- same thing is happening -- if, for example, I delete one of the numbers on the sheet, the change is not reflected in the total line.

Can someone please help!

Thanks,
Anita