首先，在VB中并没有直接提供获取文本框选中文本范围或者准确光标位置的方法，但可以通过一些间接手段巧妙地达到目的：
1、**获取当前光标位置：**
文本框有一个内置属性`SelStart`可以用来获得或设置插入点即光标的当前位置索引值。该数值表示从字符串起始处到光标之间的字符数。例如：
vbnet
Dim cursorPosition As Integer = TextBox1.SelStart
2、**获取选定的文字范围：**
同样有 `SelLength` 属性用于指示被用户选取的一段文字长度。结合上述提到的 `SelStart` ，我们可以计算出所选内容的开始及结束位置，并进一步提取这部分文本。
vbnet
' 获取选区起点
Dim selectionStartPosition As Integer = TextBox1.SelStart
' 获取选区长度
Dim selectionLength As Integer = TextBox1.SelLength
' 提取并显示选中的文本
If selectionLength > 0 Then
Dim selectedText As String = TextBox1.Text.Substring(selectionStartPosition, selectionLength)
End If
3、对于更复杂的情况如跨行的选择或是需要处理高级编辑功能时，则可能需要用到WinAPI函数进行辅助。比如使用SendMessage WinApi 函数配合特定的消息代码(EM_GETSEL) 来同时得到光标位置及其周围文本着重标记的状态:
vbnet
Private Declare Function SendMessage Lib "User32" Alias "SendMessageA" (ByVal hWnd As IntPtr, ByVal wMsg As Int32, ByRef wParam As Integer, ByRef lParam As Integer) As Integer
Public Const EM_LINEFROMCHAR As UInteger = &HC9
Public Const EM_POSFROMCHAR As UInteger = &HB6
Public Const WM_USER As UInt32 = &H400 ' User-defined messages start here.
Structure Point
Public X as Integer
Public Y as Integer
End Structure
...
Dim startPos As Integer
Dim endPos As Integer
Dim ptStruct As New Point()
'SendMessage to get the Selection Start and End positions.
SendMessage(textBox1.Handle.ToInt32(), EM_GETSEL, startPos, endPos)
'Determine line number from character position if needed using EM_LINEFROMCHAR
Dim lineNumberFromChar As Integer = SendMessage(textBox1.Handle.ToInt32(), EM_LINEFROMCHAR, startPos, 0)
'And for getting pixel coordinates of caret or specific char use EM_POSFROMCHAR
SendMessage(textBox1.Handle.ToInt32(), EM_POSFROMCHAR, CInt(startPos), ptStruct)
Console.WriteLine("Cursor at Line#: {0}, Position: ({1},{2})",lineNumberFromChar,ptStruct.X, ptStruct.Y )
以上就是在VB环境下通过标准控件属性与扩展至Windows API的方式以精确控制和取得文本框内选中区域的位置信息及光标坐标的过程，这对于开发具有丰富交互体验的应用程序至关重要。而在实际应用中还需注意异常情况下的边界检查等问题确保逻辑严谨性和稳定性。
