Trading Specific Populations

Lets say that i want to trade 15,000 HTE for some LLW with a specific country...
Could anyone tell me how to do this, i.e. the process....because up under "trade" all they seem to offer are product trades.
In addition are there generally accepted percentages for these matters....such as 1 HTE per 1.5 LLW?

while in a country, top menu bar, departments>labor>exchange professionals with others>exchange more professionals.
When u make an offer with another country the game will show if offered workers equals the asking offer of workers.

thnx