You will need at least two more tables: Buy Currency and Sell Currency. In the Buy Currency table besides what ever fields you need (date, amount, etc) set a field called, _kp_Buy CurrencyID. Make it a number field that auto generates serial numbers. This will give each of your transaction records an ID, very similar to an invoice number. It is called a primary key. Also create _kf_Customer Name. For every transaction there should be a customer associated with it. For the Buy Currency table all you need is the name. The in Database management dialog, go to the relationship tab and link _kf_customer name in BUy Currency table to Customer name in the Customer table.
In a layout pulling data from customers. Insert a portal that pulls records from Buy Currency. Sort it on _kp_Buy_Curreny_ID in descending order and select how many rows you want (aka how many records you want displayed). Put what ever fields you need in that portal. Since it is sorted in descending order the latest transaction by a customer will be first in the portal.
This is just a general instructions to set up what you are looking for. Adjust as necessary. Hope this helps. A book on FileMaker mite be more usefully when you first start then the forum. FileMaker Bible is pretty good.
Thanks for the suggestions / help. I think I need to do alot more reading and some worked examples of easier tasks to build up to what I need to achieve - however I will try and interpret your instructions then ask agian if I may?