Outcome #N/A; conditional format

Hi, when I lookup values from a table, I get three different outputs:

- a date when a training is completed.

- '0' when a training is not yet completed.

- '#N/A' when a training is not started.

The '0' I can mask with a conditional format, however the '#N/A' not.

How can I prevent the '#N/A' to be visible in my outcome?