Defaulting the Account screen 'Region' field.

Within the Account screen there is a Region field which currrently has a drop down list box, and a description field next to it. I need to change this so that, using the country code + Other fields the Region value and description is looked up from Z tables (joined) from within R/3. I already have a functional module that I can remotely call which will allow the source values to be parsed to R/3 and will extract the Region value and description and return this. However, where should this code reside, and more to the point, how can I discover myself where I can place this code.

I therefore have a number of questions around this:

o Is calling a remote FM, the best solution, as I know that R3 data can be accessed from CRM.

o I can look at the fields for this assignment block of the Accounts screen (if that's the right terminology) and can see the 'Region' field and next it the 'Name' field. However, one of the other fields, like language, also a field next to it called 'Name', so how can that be right?.

o How can I populate the Region description field (called 'Name').

Any help would be greatly appreciated.

Jason