undo

I have a small problem which I hope you can help me with I have a RichTextBox which contains a small amount of text entered by the user I have written the code to highlight certain words as they are being entered, similar to syntax highlighting The problem is that the RichTextBox undo history...

hi please help me my project is in vb.net i am having a picture box in which i have displayed an image and apllying points and curves on it. now i want to undo that. please reply. thank you.:)