Option Explicit

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

Private Const EM_GETLINE = &HC4
Private Const EM_LINELENGTH = &HC1

Private Function ColorWords(ByRef rtb As RichTextBox, _
                           ByRef sFindString As String, _
                           ByVal lColor As Long) As Integer
On Error GoTo ErrHandler
   Dim lFindLength         As Long
   Dim lFoundPos           As Long
   Dim lTempPos            As Long
   Dim iOptions            As Integer
   Dim iMatchCount         As Integer

   ' Set search options
   iOptions = rtfNoHighlight 'used by default here
   If Check1(0).Value = 1 Then iOptions = iOptions + rtfWholeWord
   If Check1(1).Value = 1 Then iOptions = iOptions + rtfMatchCase

   ' Save the string-length
   lFindLength = Len(sFindString)

   ' Search for a single match. Find method returns
   ' the position of the first character of the item,
   ' or -1 if no matches are found.
   lFoundPos = rtb.Find(sFindString, 0, , iOptions)

   ' Loop until all occurences are found
   Do Until lFoundPos < 0
       iMatchCount = iMatchCount + 1
       rtb.SelStart = lFoundPos
       rtb.SelLength = lFindLength
       rtb.SelColor = lColor
       lTempPos = lFoundPos + lFindLength
       lFoundPos = rtb.Find(sFindString, lTempPos, , iOptions)
   Loop

   ' Return the number of matches
   ColorWords = iMatchCount
   Exit Function

ErrHandler:
   MsgBox "Unexpected error number-" & _
       CStr(Err.Number) & _
       " occurred in " & Err.Source & _
       ":" & vbCrLf & vbCrLf & Err.Description
End Function

Private Sub Command1_Click()
  ColorWords RichTextBox1, txtSearch.Text, vbRed
End Sub

Private Sub RichTextBox1_Click()

   Dim strBuffer As String
   Dim lngLength As Long
   Dim intCurrentLine As Integer
   Dim lngLineNumber As Long
       With RichTextBox1
       intCurrentLine = .GetLineFromChar(.SelStart)
       'get line length
       lngLength = SendMessage(.hwnd, EM_LINELENGTH, intCurrentLine, 0)
       'resize buffer
       strBuffer = Space(lngLength)
       'get line text
       Call SendMessage(.hwnd, EM_GETLINE, intCurrentLine, ByVal strBuffer)

       lngLineNumber = .GetLineFromChar(.SelStart)
       MsgBox "You selected line number " & lngLineNumber + 1 & " which
says " & strBuffer
   End With
End Sub