I understand that you are looking for something on these lines:
string i_clob1 = "";
string i_clob2 = "";
string i_clob3 = "";
if (message.Length >= 3 && message.Length <= 32000 * 3)
{
int lastStart = 2 * message.Length / 3;
int lastLength = message.Length - lastStart;
i_clob1 = message.Substring(0, message.Length / 3);
i_clob2 = message.Substring(message.Length / 3, message.Length / 3);
i_clob3 = message.Substring(lastStart, lastLength);
}
else if (message.Length < 3)
{
i_clob1 = message;
}