Coding for Find and Replace Function.

[SLDenman]

I am working on a project and have come to a hault. I am not sure how to code the stings for the Find and Replace function of a notepad that I have created. How do I code to have the input on a subform be found and replaced on the mainform. I know how to code to have it find one word but how do I code it find whatever the user is looking for?
I have attached a screen shot to show what the IDE looks like.

Here is the main form code:

Public Class Editor

    Private Sub ClearButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ClearButton.Click
        RichTextBox1.Clear()
    End Sub

    Private Sub ExitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitButton.Click
        Me.Close()

    End Sub

    Private Sub ColorGroupBox_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ColorGroupBox.Enter
        BlackRadioButton.Checked = True
    End Sub

    Private Sub FontGroupBox_Enter(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FontGroupBox.Enter
        CourierNewRadioButton.Checked = True
    End Sub

    Private Sub ExitToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitToolStripMenuItem.Click
        'Terminate the project.
        Me.Close()

    End Sub

    Private Sub ClearToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ClearToolStripMenuItem.Click
        'Clear the textbox.
        RichTextBox1.Text = ""
    End Sub

    Private Sub FindandReplaceButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FindandReplaceButton.Click
        FindandReplaceForm.ShowDialog()

    End Sub

    Private Sub FindAndReplaceToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FindAndReplaceToolStripMenuItem.Click
        FindandReplaceForm.ShowDialog()

    End Sub
End Class

Here is the sub form code:

  Public Class FindandReplaceForm

    Private Sub ReplaceButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ReplaceButton.Click

    End Sub
End Class

Any help is appreciated.
-Stephanie