Limits to Dimension Members for Journal Entries 
You can limit the number of dimension members that are available to users during journal entry. All base-level members that the user has access to are available when the user fills out a journal template. By using the EnableJRN property for a dimension, you can limit the members available to users when they double-click member cells in the journal template.
You can limit journal dimension member lists by adding the property EnableJRN to the dimension for which you want to limit journal access. Then, in its dimension sheet, type a Y in the EnableJRN column of base-level members for which you want to allow users to post journal entries. Repeat this for each dimension you want to limit, and process the dimensions.
You might want only some account members used for journal entries, regardless of whether the users have access to other members.