Rich Text Box Controls

Inserting text with the rich textbox control is made very simple.  It has three parts: SelStart, SelLenth, and SelText.  The SelStart is where the text is going to be inserted (in letters), and can't be longer than the the text.  SelLength is the total number of letter that will be deleted after SelStart.  SelText is the text that is going to replace the SelLength.  If SelLength is zero the SelText will just be inserted where SelStart is.

Object.SelStart = Integer
Object.SelLenth = Integer
Object.SelText = Text

'RichTextBox1 displays "Good "
RichTextBox1.SelStart = 5
RichTextBox1.SelText = "Evening"
'RichTextBox1 now displays "Good Evening

If you want to replace text I suggest you do the Replace function.  The following is how to make a replace function.

Object = Replace(String, Find, ReplaceWith, _
Start, NumerToCorrect)

Dim Temp As String
'I prefure to use a variable
Temp = RichTextBox1.Text
'RichTextBox1 displays "aaAaAAaa"
Temp = Replace(Temp, "a", "B", 2, 3)
RichTextBox1.Text = Temp
'RichTextBox1 now displays "aBABAABa"

It replaced 3 "a" with "B" starting from the second letter of Temp and then set the text back to Temp.  That is how the replace function works.  You can skip the number of times to replace, and it will replace every existence after the start.  If you skip the start, it will start searching from the beginning.