VS C# 2008 richTextBox - limiting line length?

Question

Hi to all,
I am using a richTextBox to input plain text and using streamWriter to write this text to a local file. Is it possible to  use the sendKeys.send method to cause the {enter} keystroke to be activated after a certain number of keystrokes are entered per line? I wish to limit the line length to 45 keystrokes somehow in code.
Thanks to anyone offering any suggestions.