Detect the new value added to a CustomField and add it to FixVersion

[ahmed salem]

I'm new to Jira development and I need to write a listener that does the following:

 - Whenever a new value is added to the "Target Version" custom field, this new value should be added to the native "FixVersion" field

And vice versa

 - Whenever a new value is added to the "FixVersion" native field, this new value should added to the "Target Version" custom field.

Any help would be much appreciated.

Thanks,

Ahmed.