Windows provides you with those functions automatically:
VB Code:
  1. 'cut:
  2.     RichTextBox1.SetFocus
  3.     SendKeys "^x"
  4.    
  5.     'copy:
  6.     RichTextBox1.SetFocus
  7.     SendKeys "^c"
  8.    
  9.     'paste:
  10.     RichTextBox1.SetFocus
  11.     SendKeys "^v"