Throwing error message when selecting a record inside DCL Field,

Summary

When selecting value in DCL field, we want to throw a warning message if they select a record that is outside their market.

Content

Requirement: They can select any account but if the selected account is outside their market we need to show them a warning message if they want to continue.

What we've done: We have a DCL field where they can select an account.

Question:

1. Is it possible to show a warning when selecting a value inside the DCL field? This is after they click the OK button.