I don't know anything about the Stephan Lebans RTF2 ActiveX Control but you it seems you're being ignored so I thought I'd see if I could give you something. I've had to deal with rich text before, trying to get it from Access into Word with limited success partly because the HTML that you get out of rich text doesn't contain all of the information that was in the rich text.
Anyway I played with this with Access's rich text controls in the attached database and to my surprize I got something that seems to work. In the attached database you will find a form (RTF Form 1) which has a subform (RTF Subform 2) and a command button (Append Text) whose click event has the following code.
Private Sub AppendText_Click()
Dim db As DAO.Database
Set db = CurrentDb
db.Execute "UPDATE [RTF Table 1] SET [RTF Table 1].[Rich Text] = '" & SQE(Me.Rich_Text) & SQE(Me.RTF_Subform_2.Form![Rich Text]) & "'"
Private Function SQE(str As String) As String
SQE = Replace(str, "'", "''")
So this just basically updates the control source of the RTF control with the text in it concatenated with the text in the subform and refreshes the form. If you can adapt this to your situation I suggest testing it thoroughly to make sure formatting isn't lost in this transfer.
Let us know this helps.