Mandatory custom field on resolve only

Hi everybody,

Is it possible to have mandatory custom field on resolve only. I realize
that I can’t create a standard mandatory CF as it would make it mandatory on

I tried to do it via scrips, but it works halfway. The ticket remains open
but no error message is displayed, which is confusing.

If you have example or documentation on how I could accomplish this it would
be appreciated. I googled it but didn’t found anything useful :frowning:

If possible, I’d also like to have a code snippet on how to display result
on top of the page.

Thank you very much.