How to add custom script to DB Health Check? (4241533)

I want to add a custom script for the database size (select sum(bytes) from dba_segments;)  into the Database Health Check item.  How can I do this?
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Please follow the step below:

1.  Save your query (select sum(bytes) from dba_segments;)  into a file.

2.  Then go to the Database | Diagnose | DB Health Check

3.  Go to  "Check and Option" tab | Setting and check the option "Play a custom script at the end of the health check".

4.  Then click on the "Params" and point to your custom script for the database you want to run.