I am using the following formula in all my first hundred rows for column F:

```
=(E5-D5)*1440
```

This is used to calculate the time in minutes between the cells in column E and column D. I have this formula applied to every row. The formula works however I have rows where the E and D columns are empty. For these Excel displays a 0 in column f.

Is there a way I can make a number format show nothing if the value of the cell is zero? Note that I still want to keep this as a number formatted cell as later on I sum up all the values in column f and use that in another part of the spreadsheet.