Public Class Form1
 
Private Sub Form1_Load( ByVal sender As System.Object,  ByVal e As _
  System.EventArgs) Handles MyBase.Load
    Edit.Text = "test hallo test"
End Sub
 
Private Sub Test
    Dim txt     as String       = Edit.Text
    If Len(txt)=0 then Exit Sub
 
        For i As Integer = 1 to Len(txt) step 1
 
            If Not i + Len("hallo") > Len(txt) then
                If Mid(txt,i,Len("hallo")) = "hallo" then
 
                    Dim selstart As Long = Edit.SelectionStart
 
                    Edit.SelectionStart=i-1
                    Edit.SelectionLength=Len("hallo")
                    Edit.Select
                    Edit.SelectionColor=Color.Blue
 
                    Edit.SelectionStart=selstart
                    Edit.SelectionLength=0
 
                End If
            End If
 
        Next i
 
End Sub
 
Private Sub Edit_TextChanged( ByVal sender As System.Object,  ByVal e As _
  System.EventArgs) Handles Edit.TextChanged
        Test
End Sub
 
 
End Class