I am trying to build a basic banking application in Salesforce for personal practice purpose. I am a beginner to Salesforce and I am trying to do this by only the Declarative Abilities as I have not started with Apex Developement yet.

These are the requirements for the app:

1. There are 5 members (accounts) who each have an available balance.
2. There is a System balance which is the total of the balances of all the members.
3. The Members can perform transactions of a few types, Credit, Debit, Interest Paid, etc.
4. There is an additional rquirement where one must select all the members together (or any number of members) and perform the transaction which effects each account equally. (say $100 deducted from the 5 selected accounts would deduct $20 from each)

So the problem I am facing is to align these requirement in the Object model that Salesfore has. This would have been quite simple to write in any programming language as it would be variable dependant. In this case when I try to use only the Declarative Abilities, the design is proving difficult.

If I create separate Objects for Members, System and Transactions, how can I select more than one Member at a time (which is not possible with Master-Detail or Lookup).

If someone reading this can give me a brief idea about the design which could be used in this case then it would be great!
And if this cannot be achieved without VF pages then that would also be good to know.

Thanks!