Public Class Form1
    Dim KeyWord As String = "aid"
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TextBox1.Text = "Now is the time for all good men to come to the aid of their country the quick brown fox jumps over the lazy dog"
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Ary() As String = Nothing
        Ary = TextBox1.Text.Split(" ")
        Dim index As Integer = 0
        For index = 0 To UBound(Ary)
            If Ary(index) = KeyWord Then
                Exit For
            End If
        Next
        If index <= UBound(Ary) Then
            For i As Integer = index - 10 To index - 1
                TextBox2.Text &= Ary(i) & " "
            Next
            For i As Integer = index + 1 To index + 10
                TextBox3.Text &= Ary(i) & " "
            Next
        End If
    End Sub
End Class

Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TextBox1.Text = "The quick brown fox jumps over the lazy dog" & vbNewLine
        TextBox1.Text &= "Now is the time for all good men to come to the aid of their country" & vbNewLine
        TextBox1.Text &= "This is a test for finding all."
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim ary As String()
        ary = TextBox1.Text.Split(vbNewLine)
        For index As Integer = 0 To UBound(ary)
            If ary(index).IndexOf("the") <> -1 Then
                MessageBox.Show(ary(index))
            End If
        Next
    End Sub
End Class