Conditionally populate custom field value when adding linked issue?

[Teja]

Hi Team,

I was hoping to get help on this.
I need to conditionally populate 'Caused By' cf [Single select list] value, when adding an "is caused by" link of issue to the linked issue.

For example:- When adding an "is caused by" relationship link on the transition screen, if the "Caused By" field is "None" or "Caused By Not Considered" populate the "Caused By" based on the type of issue being linked.

Caused By values are "Bug Fix", "Customization", "Caused By Not Considered", None.

If the linked issue project is GTBUG => set to Bug Fix
If the linked issue project is PSO => set to Customization

Thanks in advance

[Teja]

Any help?