[求助]如何返回VB6中TextBox中某一行的字符？

cag

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Function GetLineText(CTextBox As TextBox, LineIndex As Long) As String
　Dim lc&, linechar&
　linechar = SendMessageBynum(CTextBox.hwnd, EM_LINEINDEX, LineIndex, 0)
　lc = SendMessageBynum(CTextBox.hwnd, EM_LINELENGTH, linechar, 0) + 1
　GetLineText = String$(lc + 2, 0)
　Mid$(GetLineText, 1, 1) = Chr(lc And &HFF)
　Mid$(GetLineText, 2, 1) = Chr(lc \ &H100)
　lc = SendMessageBystring(CTextBox.hwnd, EM_GETLINE, LineIndex, GetLineText)
　GetLineText = left(GetLineText, lc)
End Function

如上函数，如何声明SendMessageBynum和SendMessageBystring???

谢！