How to access binary type field in MSSQL 2000 with Delphi 6 Ent

Hello, all,
    I use ADOQuery or ADOCommand to update or insert data into a binary
field in MS SQL 2000. But when I assign value to the parameter like this:
    ADOCommand1.Parameters.ParamByName('BinField').Values := SomeData;
it always report error.
I tried many times and still can't know which proper data type should the
var 'SomeData' be. In other words, how can I assign value to a parameter of
a binary type field?

Can anyone help me? Thanks in advance.