Len(RichTextBox1.Text),RichTextBox1.SelText = a 觉得有问题,象下面这样处理就不会出错了:
Private Sub Command1_Click()
Open "C:\123.txt" For Input As #1
While Not EOF(1)
Line Input #1, a
RichTextBox1.SetFocus
SendKeys "^{end}"
RichTextBox1.SelRTF = a
Wend
Close #1
Me.Caption = Len(RichTextBox1.Text)