When using a RichTextBox there are 2 copies of the Text, there is a straight Text Version and a Formated RTF copy, when performing operations on Characters within the Text, make sure you're using the .Text Property, otherwise it'll use the RichText Formatted Copy by Default and You'll be manipulating the Formatting characters along with the Text giving the Unexpected results you are experiencing.

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Aaron Young
Analyst Programmer
[email protected]
[email protected]