Diana, I assume you have a relationship between BO and CLASS Object, perhaps as "Peer".
Then in your rule, you can always get Class's Description and assign it to BO.Description.
For example, if you only want this to happen when BO is NEW, you can say,
IF BO IS NEW AND BO.Class IS DEFINED Then BO.Description = Class.Description.
And then for this rule, in advance tab, set the Dynamic rule on to show on the form immediately.
In here, I get a drop down of course templates (like your classes)

Once I select it, then I get the "# of days" (like your Class description) and put it in my main BO.
