Hi,
By default this solution will list all items – both files and folders that matches with the query, but you can change your CAML like this to have it only list folders initially:
<Where>
<And>
<Eq><FieldRef Name='FSObjType' /><Value Type='Integer'>1</Value></Eq>
<Eq><FieldRef Name='SPCustomerAccountID' /><Value Type='Text'>[currentItem:ID]</Value></Eq>
</And>
</Where>
Let me know how this works out.
Alexander