求解 VB中sellength获取字符串太慢怎么处理

求解 VB中sellength获取字符串太慢怎么办
我用richtextbox打开一个文件，要做更改字体颜色的功能
但richtextbox是要先选择文本的，所以用richtextbox1.sellength=len(richtextbox1.text)
但是很慢怎么办，文件小点还好，要是有几万字的就直接卡死了。
本人初学不久，数次上网搜索无解，只能求高手解答，必当感激不尽

[解决办法]

VB code

Option ExplicitPrivate Const VK_CONTROL = &H11Private Const KEYEVENTF_KEYUP = &H2Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)Private Declare Sub keybd_event Lib "user32" (ByVal bVk As Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As Long)Private Sub Command1_Click()    Dim lngP As Long    RichTextBox1.SetFocus    keybd_event VK_CONTROL, 0, 0, 0     '按下Ctrl键    keybd_event &H41, 0, 0, 0           '按下A键    Sleep 500                           '延时500毫秒    keybd_event &H41, 0, KEYEVENTF_KEYUP, 0         '释放A键    keybd_event VK_CONTROL, 0, KEYEVENTF_KEYUP, 0   '释放Ctrl键End SubPrivate Sub Form_Load()    Dim intP As Integer    Dim intT As Integer    For intP = 0 To 50        For intT = 0 To 50            RichTextBox1.Text = RichTextBox1.Text & "哈哈哈哈哈哈哈哈哈哈哈"        Next intT    Next intPEnd Sub