Updating blob field in an interbase table

I am trying to update a Blob field in a interbase table with data from a
TMemo component using the SQL Update command eg.  below is just an example

SQL.Add('Update aTable');
SQL.Add('SET aBlob = :MemoData'); { -- aBlob = a Blob field in a interbase
table }
Prepare;
Params[0].AsString := aMemo.Lines; { -- aMemo is a TMemo component }

I know the Params line is not correct and I hope someone can show me a way of
performing the above
function correctly.

Thanks in advance.

David Lee.