How to emulate WRITETEXT / Writing to LONG fields

I am working on porting a Delphi / SQL Server application to Oracle
8i.

In one instance of the program we have a RTF Memo field and we save
its lines property directly to a TEXT field using WRITETEXT.

What SQL statement could I use under ORACLE that would provide me with
the same results?

Thanks... Jeff

//Sample DELPHI code underneath. Need to translate SQL statement for
Oracle.

StrStrm := TStringStream.Create('');
Text.SaveToStream(StrStrm); //this is actually the memo.lines

CommandExec('DECLARE @ptrval varbinary(16) '+
'SELECT @ptrval = TEXTPTR(['+FieldName+'])'+
' FROM '+TableName+
' WHERE '+WhereClause+
' WRITETEXT '+TableName+'.'+FieldName+' @ptrval
'''+PChar(StrStrm.DataString)+'''')