How can I prevent users from creating an issue based on a ready-only custom field?

[Andrea C]

In the Jira Service Desk portal, I have an autocomplete field that will populate other read-only fields. I then have another read-only field that will generate a positive or negative response based on the result of one of the read-only fields.

I would like to prevent users from creating an issue (maybe by greying out the create button?) if a read-only field displays a specific value.

Ideally, I would like to do it before the user click on "create" but I don't know if it's possible (maybe with ScriptRunner?). If not possible, I am happy to check the value with a validator and return an error, but I am not sure how to do both.

Thanks.