Private Type BookInfo
    Title As String
    ISBN As String
    URL As String
End Type
Private MaxBook As Integer
Private BookInfos() As BookInfo

When the program unloads, it calls SaveData to write the data back into the file.

' Load the data from a file.
Private Sub LoadData()
Dim fnum As Integer
Dim fname As String
Dim i As Integer

    fnum = FreeFile
    fname = App.Path & "\books.txt"
    Open fname For Input As #fnum

    Input #fnum, MaxBook
    ReDim BookInfos(0 To MaxBook)

    For i = 0 To MaxBook
        With BookInfos(i)
            Input #fnum, .Title, .ISBN, .URL
        End With
    Next i

    Close #fnum
End Sub

' Save the data into a file.
Private Sub SaveData()
Dim fnum As Integer
Dim fname As String
Dim i As Integer

    fnum = FreeFile
    fname = App.Path & "\books.txt"
    Open fname For Output As #fnum

    Write #fnum, MaxBook

    For i = 0 To MaxBook
        With BookInfos(i)
            Write #fnum, .Title, .ISBN, .URL
        End With
    Next i

    Close #fnum
End Sub

' Load data into the control.
Private Sub DBGrid1_UnboundReadData(ByVal RowBuf As _
    MSDBGrid.RowBuffer, StartLocation As Variant, ByVal _
    ReadPriorRows As Boolean)
Dim dr As Integer
Dim row_num As Integer
Dim r As Integer
Dim rows_returned As Integer

    ' See which direction to read.
    If ReadPriorRows Then
        dr = -1
    Else
        dr = 1
    End If

    ' See if StartLocation is Null.
    If IsNull(StartLocation) Then
        ' Read from the end or beginning of
        ' the data.
        If ReadPriorRows Then
            ' Read backwards from the end.
            row_num = RowBuf.RowCount - 1
        Else
            ' Read from the beginning.
            row_num = 0
        End If
    Else
        ' See where to start reading.
        row_num = CLng(StartLocation) + dr
    End If
    
    ' Copy data from the array into RowBuf.
    rows_returned = 0
    For r = 0 To RowBuf.RowCount - 1
        ' Do not run beyond the end of the data.
        If row_num < 0 Or row_num > MaxBook Then Exit For

        ' Copy the data into the row buffer.
        With BookInfos(row_num)
            RowBuf.Value(r, 0) = .Title
            RowBuf.Value(r, 1) = .ISBN
            RowBuf.Value(r, 2) = .URL
        End With

        ' Use row_num as the bookmark.
        RowBuf.Bookmark(r) = row_num

        row_num = row_num + dr
        rows_returned = rows_returned + 1
    Next r

    ' Set the number of rows returned.
    RowBuf.RowCount = rows_returned
End Sub

' Save data updated by the control.
Private Sub DBGrid1_UnboundWriteData(ByVal RowBuf As _
    MSDBGrid.RowBuffer, WriteLocation As Variant)
    ' Update only the values that have changed.
    With BookInfos(CInt(WriteLocation))
        If Not IsNull(RowBuf.Value(0, 0)) Then _
            .Title = RowBuf.Value(0, 0)
        If Not IsNull(RowBuf.Value(0, 1)) Then _
            .ISBN = RowBuf.Value(0, 1)
        If Not IsNull(RowBuf.Value(0, 2)) Then _
            .URL = RowBuf.Value(0, 2)
    End With
End Sub

' Delete an entry.
Private Sub DBGrid1_UnboundDeleteRow(Bookmark As Variant)
Dim r As Integer

    ' Fill in the hole.
    For r = Bookmark + 1 To MaxBook
        BookInfos(r - 1) = BookInfos(r)
    Next r

    MaxBook = MaxBook - 1
End Sub

' Add a new entry.
Private Sub DBGrid1_UnboundAddData(ByVal RowBuf As _
    MSDBGrid.RowBuffer, NewRowBookmark As Variant)
    ' Make room for the new entry.
    MaxBook = MaxBook + 1
    ReDim Preserve BookInfos(0 To MaxBook)

    ' Set the bookmark to the new entry.
    NewRowBookmark = MaxBook

    ' Save the new data.
    With BookInfos(MaxBook)
        If Not IsNull(RowBuf.Value(0, 0)) Then
            .Title = RowBuf.Value(0, 0)
        Else
            .Title = DBGrid1.Columns(0).DefaultValue
        End If
        If Not IsNull(RowBuf.Value(0, 1)) Then
            .ISBN = RowBuf.Value(0, 1)
        Else
            .ISBN = DBGrid1.Columns(1).DefaultValue
        End If
        If Not IsNull(RowBuf.Value(0, 2)) Then
            .URL = RowBuf.Value(0, 2)
        Else
            .URL = DBGrid1.Columns(2).DefaultValue
        End If
    End With
End Sub

' Add a new record.
Private Sub cmdAdd_Click()
    MaxBook = MaxBook + 1
    ReDim Preserve BookInfos(0 To MaxBook)
    With BookInfos(MaxBook)
        .Title = txtTitle.Text
        .ISBN = txtISBN.Text
        .URL = txtURL.Text
    End With

    DBGrid1.Refresh
End Sub