The first bit of advice I can offer you is that you should try to avoid VB6's built-in objects: most of them are well programmed, but they're very abstracted, and so you'll never have complete control over them without hecking into their message queues... at which point, you would have done well to just roll your own controls in the first place. =)
But, if you simply must use the built-in objects, let me help you.
First, don't use the character '/' as a tag. Instead, I recommend that you use html-esque tags; in this case, our interpreter will make all the text between the tags <green> and </green> be green.
So, here's the function you're going to want to use: it reads in a line of text, and outputs rtftext which can be set to a richtextbox's textrtf property. =)
Private Function sGetRTFText(ByVal nText As String) As String
Dim iLines() As String, i As Long
Dim iWords() As String, j As Long
Dim iThisLine As String, iFollowingTag As Long
nText = Replace(nText, vbCrLf, "<br>", , , vbTextCompare)
nText = Replace(nText, "<", " <", , , vbTextCompare)
nText = Replace(nText, ">", "> ", , , vbTextCompare)
iLines = Split(nText, "<br>", , vbTextCompare)
For i = LBound(iLines) To UBound(iLines)
If iLines(i) <> vbNullString Then
iWords = Split(iLines(i), " ", , vbTextCompare)
For j = LBound(iWords) To UBound(iWords)
If iWords(j) <> vbNullString Then
Select Case LCase(iWords(j))
Case "<green>"
iThisLine = iThisLine & "\cf1 "
Case "</green>"
iThisLine = iThisLine & "\cf0 "
iFollowingTag = 1
Case Else
iThisLine = iThisLine & iWords(j) & " "
End Select
End If
Next j
sGetRTFText = sGetRTFText & iThisLine & "\par "
iThisLine = vbNullString
End If
Next i
'add the header, the font table, and the color table.
sGetRTFText = "{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\fswiss\fcharset0 Arial;}}" & _
"{\colortbl ;\red0\green128\blue0;}" & sGetRTFText & "}"
End Function
A good test of this code's functionality would be to try this:
rtfOutput.TextRTF = sGetRTFText("Some test text:<br>Hello World!<br>This word is <green>green</green>!")
