Remove end character in a textbox without rewriting all the data - vb.net

Question

I am writing a program to communicate over the serial port. All data that is sent is mirrored back. Everything works fine except backspaces. When I hit the backspace button the only way I know how to remove the last character in the text box is to use a mid function then overwrite the current data with the new data. When a lot of data is inside the richtextbox it starts to flicker. I have tried using the richtextbox.text.remove function but I get this error. "Index and count must refer to a location within the string. Parameter name: count"
RichTextBox1.Text.Remove(RichTextBox1.TextLength, 1)
I have tried to throw some number into the function that does not cause it to error out but no data is removed from the richtextbox.
Here is the code that transmits data
KeyCharString = e.KeyChar 'stores key being pressed into KeyCharString
Try
SerialPort1.Write(KeyCharString) 'tx data for key being pressed
Catch ex As Exception
MsgBox(ex.Message) 'Displays error if serialport1 cannot be written to
End Try
If Asc(KeyCharString) = 8 Then 'If char is a backspace remove precious character and exit sub
RichTextBox1.Text = RichTextBox1.Text.Remove(RichTextBox1.TextLength, 1)
'RichTextBox1.Text = Mid(RichTextBox1.Text, 1, RichTextBox1.TextLength - 1)'Old code used to remove the character. Causes the richtextbox to flicker when rewriting the data
Exit Sub
End If
This is the code that receives data
receivedString = SerialPort1.ReadExisting.ToString
If Asc(receivedString) = 8 Then 'deletes the received data if it is a backspace
receivedString = ""
Exit Sub
End If
RichTextBox1.AppendText(receivedString) 'adds new data to the richtextbox
Is there a way to remove 1 character from the richtextbox without rewriting all the data inside it? Also, the richtextbox is read only.

Answer 1

The String.Remove method that you are using returns a String it does not do anything with the original string.
from MSDN Link:
Returns a new string in which all the characters in the current instance, beginning at a specified position and continuing through the last position, have been deleted.
Try this but I am not sure of the flicker:
RichTextBox1.Text = RichTextBox1.Text.Remove(RichTextBox1.TextLength - 1, 1)
or something like this:
RichTextBox1.SelectionStart = RichTextBox1.TextLength - 1
RichTextBox1.SelectionLength = 1
RichTextBox1.ReadOnly = False
RichTextBox1.SelectedText = ""
RichTextBox1.ReadOnly = True