Have a look at StringVariable.SubString (or the older InStr) and StrConv in the RichTextBox TextChanged event. Something like:
vb Code:
Const autoCaps As String = ". "
Private Sub RichTextBox1_TextChanged(sender As System.Object, e As System.EventArgs) Handles RichTextBox1.TextChanged
If Me.RichTextBox1.SelectionStart > 3 Then
If Me.RichTextBox1.Text.Substring(Me.RichTextBox1.SelectionStart - 3, 3) = autoCaps Then
Me.RichTextBox1.Text = StrConv(Me.RichTextBox1.Text, VbStrConv.Uppercase)
End If
End If
End Sub
Chris.