How to check if a specific field is existing on another project by using scriptrunner in jira?

[John Paul Manalili]

Hi! Good day, I would like ask if you have any idea/ideas on how to create a custom script using scriptrunner? I'm new to scriptrunner and would like to do a workflow validator wherein if the value that is being typed is matched on another field in another project. For example (if the value that is being type on customfield B in Project B is match on the existing data of customfield A in Project A). If it's matches, then it will proceed in creating a ticket otherwise it will give a error message.