Public Function ValidateActionUI(action_str As String) As String
To validate what the user has entered in your controls for an event action, return a non-empty string error message from this procedure. After a user clicks OK in the event action properties, this function is called. The parameter is the actual action string that HS will store in the event. You can validate the information and return an error string if the data is formatted incorrectly. HS will display the error string in red at the top of the event action page and will remain on the event action page. If the returned string is empty, then the action will be saved and the dialog closed.