近日研究文本控件和字符串，研究得头混脑胀，问题真是太多了。
这只是其中的一个问题，答案来自问专家网站和CSDN的TechnoFantasy(www.applevb.com) ，解决如下：
Public Const WM_USER = &H400
Public Const EM_SETTARGETDEVICE = (WM_USER + 72)
Public Declare Function GetDC Lib "user32" (ByVal hWnd As Long) As Long
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hWnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
lParam As Any) As Long
Public Sub AutoSwitchLine(ByRef RichText As Long, ByVal bSwitch As Boolean)
If bSwitch Then
'设置 RichTextBox 自动换行
Call SendMessage(RichText.hWnd, EM_SETTARGETDEVICE, _
GetDC(RichText.hWnd), RichText.Width / 15)
If RichText.RightMargin = 0 Then
RichText.RightMargin = 1
Else
RichText.RightMargin = 0
End If
Else
'设置 RichTextBox 不自动换行
Call SendMessage(RichText.hWnd, EM_SETTARGETDEVICE, 0, 1)
End If
End Sub
