I don't know about you but personally I use Vidalia to connect to TOR network, if you don't know about it, its a project that combines the TOR's required application and give you a ready to go package, here is the method that works fine to me:
Run TOR of course and go to the Vidalia control panel > click on 'View the Network' > from there you have a visual presentation of all TOR exit nodes where you can sort by flag 'simply by clicking in the top of the flag column,just do it' .. now you have all current working tor exit nodes, just find those in the country you like and write in a notepad the names of all of these servers in that country > now, back again the the Vidalia control panel and click settings > from there click on Advanced tab where you will find the full settings about tor > click on brwose, choose the file 'torrc' and choose edit > there type the following 2 lines [[[[
ExitNodes servername#1, servername#2, servername#3, servername#4, servername#5 ....etc
StrictExitNodes 1
]]]]
replace these servername#x with the server name you previosuly wrote in notepad
close after saving everything, restart and enjoy!
now, each time TOR would like to change your IP randomly it will be forced by the configuration file to a preset number of servers only, all of these servers you chose from a specific country of your choice
I would recommened that you add more servers from that country each couple of hours or days even to avoid bad nodes, or just add nodes with good performance