Always enclose in quotes any ranges containing ".." that you type directly into a formula or into a parameter with the Excel function wizard.
Without quotes, Excel may interpret your range as a set of values from the worksheet.
This functionality of Excel has nothing to do with Jet Reports. However, Jet Reports users are more likely to accidentally enter a range that causes Excel to perform a long calculation because of the way ranges of values are entered using ".."
If a formula references a cell that contains a range with ".." you do not need to type the quotes into the cell. The quotes are only required when you put the range directly into a function parameter.