I want to show the description of the Change Type on the current Change form, to help users when they are not sure what each Change Type is used for when they select from the drop-down pick list. Because the BO is Type of Change, I don't know how to pull in the description.
This requires a little bit of configuration; first, you would need to create a new text field on the Change object to store the value.
Please see the configuration below: I have named it 'TypeOfChangeDefinition' and it is unlimited Unicode text field, like the source field on the Type of Change object.
We then add a business rule to populate this field whenever the Type of Change value is set; it then pulls the description field across from that object.
On change of the 'Type of Change' field, update the 'TypeOfChangeDefinition' field, and set it to the 'Description' of the selected 'Type Of Change' (this can be added by navigating to the 'ChangeTypeOfChange -> Fields' folder in the toolbox on the right, and clicking or dragging the Description field into the expression editor).
Once this is set up, you can add the 'TypeOfChangeDefinition' field to the form.
Please note that it will only work for new records, as it is triggered on change of the Type of Change field (or if you update that field on an existing record).