If you simply want it to display the values in thousands (not actually round
the underlying values):
1. Select all the values you want to format.
2. From the FORMAT menu, choose CELLS.
3. On the NUMBER tab, choose CUSTOM in the Category list.
4. In the TYPE box, enter #,### (or 0,000)
5. Click on the OK button.
Now all the cells will display as thousands, but keep their true values:
A1 = 1,234,567
Cell A1 will display 1,234 but still keeps its full value.