Forms :: Command Line Like Interface In A Windows Form?

I am working on an application and I want the user to be able to enter commands into a textbox, and when they press enter, the command is printed in a rich text box, executed, and the output is printed. For instance: the user types move{file1}, {location} into the text box and this happens:

>command: move{file1}, {location}
>$ moving file1 to location
>job completed

How would I write lines to the rtb and execute commands when the enter key is pressed?

This works, partly.
Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles command.KeyPress
If e.KeyChar = Microsoft.VisualBasic.ChrW(Keys.Return) Then
RichTextBox2.Text = Environment.NewLine + command.Text
End If
End Sub

it erases everything in the textbox before adding the line... I would also like to be able to make a database of commands, maybe a .dll or something, so that when the user types in something, it checks that database to see if the command exists, if it does it executes, if not, error.