Multibyte characters over the frontend/backend protocol

I am trying to add multi-byte character support to the Smalltalk
PostgreSQL driver, and I would really apreciate a bit of help in
inderstanding the form in which I need to send things to the backend.

I create a database using: "create database multibytetest with encoding
= ''KOI8'';"

I can see that it has been created OK using "psql -l"; I see: "
multibytetest | bbadger | KOI8"

I create a table using: "create table test(string VARCHAR(3));"

Now, here's where I don't know what to do. I want to insert into the
new table using something like:
"insert into test values ("xyz");"
... but where "xyz" is really the KOI8 charaters 0x0422 0x0423 and 0x0416

The question is, what bytes should be sent in the String data type of
the Query message I send to the back end?

If I make the whole string multi-byte, I get a sytax error at or near "i".

Pointers to documentation or functions in existing code would be much
apreciated. Thanks.