The formula failing is the following:

```
=IF(TIMEVALUE(C2 & ":00") > TIMEVALUE(B2 & ":00"); 0; C2-B2)
```

I previously tried

```
=IF(C2 > B2; 0; C2-B2)
```

but this also gives me "Error 502".

The cells it is referring to contains data in the format "12:30" (I formatted the columns with format "HH:MM").

I just want to calculate how much time lies between two times, respecting the special case where endtime < starttime.