Total number of lines in RichTextBox

Check if this helps
http://www.codeproject.com/cs/miscctrl/numberedtextbox.asp

Also you can refer to this link
http://msdn2.microsoft.com/en-us/library/system.windows.forms.richtextbox.getlinefromcharindex(VS.80).aspx

I've looked at the first link above before and the second I've seen also.  I'll look more into these and see if I can find what I need.  By both of your comments, if I can get the line numbers I can tell what line the textbox ends on.  

Found a way to do it using Font Measurement.

                   // Create dummy string for measurement
                   String^ text = "TEST STRING";
                   System::Drawing::Font^ textFont = tbReader->Font;
                  
                   //Specify a fixed width, but let the height be "unlimited"
                   SizeF^ layoutSize = gcnew SizeF((float)tbReader->Width,
                         (float)5000.0F);
                   Graphics^ g = Graphics::FromHwnd(tbReader->Handle);
                   SizeF^ stringSize = g->MeasureString(text, textFont, (SizeF)layoutSize);

                   // Divide RTB height by font height to determine how many it can hold.
                   int numLines = tbReader->Height / stringSize->Height;

                   // Return the number
                   return numLines;