Private Const EM_CHARFROMPOS& = &HD7
Private Type POINTAPI
X As Long
Y As Long
End Type
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
Public Function RichWordOver(rch As RichTextBox, X As Single, Y As Single) As String
Dim pt As POINTAPI
Dim pos As Integer
Dim start_pos As Integer
Dim end_pos As Integer
Dim ch As String
Dim txt As String
Dim txtlen As Integer
pt.X = X \ Screen.TwipsPerPixelX
pt.Y = Y \ Screen.TwipsPerPixelY
pos = SendMessage(rch.hWnd, EM_CHARFROMPOS, 0&, pt)
If pos <= 0 Then Exit Function
txt = rch.Text
For start_pos = pos To 1 Step -1
ch = Mid$(rch.Text, start_pos, 1)
If Not ((ch >= "0" And ch <= "9") Or (ch >= "a" And ch <= "z") Or (ch >= "A" And ch <= "Z") Or ch = "_") Then Exit For
Next start_pos
start_pos = start_pos + 1
txtlen = Len(txt)
For end_pos = pos To txtlen
ch = Mid$(txt, end_pos, 1)
If Not ((ch >= "0" And ch <= "9") Or (ch >= "a" And ch <= "z") Or (ch >= "A" And ch <= "Z") Or ch = "_") Then Exit For
Next end_pos
end_pos = end_pos - 1
If start_pos <= end_pos Then RichWordOver = Mid$(txt, start_pos, end_pos - start_pos + 1)
End Function

Private Sub Form_Load()
Label1.Caption = ""
RichTextBox1.Text = "Ready-To-Run Visual Basic Algorithms, Second Edition" & vbCrLf & vbCrLf & "Extend your applications with powerful algorithms written in Visual Basic. Sorting, searching, trees, hashing, advanced recursion, network algorithms, object-oriented programming, and much more. Visual Basic Algorithms updated and expanded for Visual Basic 5." & vbCrLf & vbCrLf & "http://www.vb-helper.com/vba.htm"
End Sub

Private Sub RichTextBox1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Dim txt As String
txt = RichWordOver(RichTextBox1, X, Y)
If Label1.Caption <> txt Then Label1.Caption = txt
End Sub