not exactly Excel, but spreadsheet by OpenOffice, whenever I choose to select a set of numbers it "sometimes" calculates the sum for me in the bottom status bar, but many time it doesn't.
Is it the problem of the formatting of the number? What should I do?
When this happens in Excel it’s because the values are seen as text and not numbers. You have the option to highlight the the range and select convert to number. Another way to show this is insert another column and creat a formula that references the original column and multiples by 1, for example =A1*1. The new column will behave like numbers while the original behaves like text.
I don’t use OpenOffice but my guess is your data set is being imported as text and not a number.
The field in the Status Bar shows "Cell or object information".
It displays information about the selected items. When a group of cells is selected, the sum of the contents is displayed by default; you can right-click on this field and select other functions, such as the average value, maximum value, minimum value, or count (number of items selected). It can also be set to show nothing.