You'll need to write a custom field type add-on to do that, but I'd strongly recommend using one of the addons in the marketplace that can do it. Script Runner can do scripted fields, and it's the only one I'm familiar with. You may find others suit you better though.
Atlassian Summit is an excellent opportunity for in-person support, training, and networking.Learn more
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG