Hi bueearth,
there is a sticky thread in another subforum, please have a look at it:
http://rapid-i.com/rapidforum/index.php/topic,2190.0.htmlIf you have any further questions, please ask. Btw, if you are using a learner which is capable of handling weights, you can simply create a weights attribute (use Generate Attribute with sth. like "if(label="A",10,1)" to produce a new attribute which is 10 for class "A" and "1" for all other cases, call the new attribute "weight", and the use Set Role to define the new attribute as weight.
Best, Marius