I am displaying data from a MySQL database in a GridView.
All is cool with this code:
Code:
    Private Sub GetBooksUsageTime(ByRef UserID As String)
        Dim myDataAdapter As MySqlDataAdapter
        Dim myDataSet As New DataSet
        Dim strSQL As String
        con = New MySqlClient.MySqlConnection("Server=" + _host + ";User Id=" + _user + ";Password=" + _pass + ";")

        Try
            con.Open()
            'Check if the connection is open
            If con.State = Data.ConnectionState.Open Then
                con.ChangeDatabase("eBuki")

                strSQL = "SELECT isbn, start, end  FROM bookstime WHERE userid ='" & UserID & "'" ' ORDER BY grade"
                myDataAdapter = New MySqlDataAdapter(strSQL, con)
                myDataSet = New DataSet()
                myDataAdapter.Fill(myDataSet)

                gvBookTime.DataSource = myDataSet
                gvBookTime.DataBind()
                gvBookTime.HeaderRow.Cells(0).Text = "Book"
                gvBookTime.HeaderRow.Cells(1).Text = "Start Time"
                gvBookTime.HeaderRow.Cells(2).Text = "End Time"
                gvBookTime.HeaderRow.Cells(3).Text = "Total Time"

                gvBookTime.HeaderRow.Cells(0).HorizontalAlign = HorizontalAlign.Left
                gvBookTime.HeaderRow.Cells(1).HorizontalAlign = HorizontalAlign.Left
                gvBookTime.HeaderRow.Cells(2).HorizontalAlign = HorizontalAlign.Left
                gvBookTime.HeaderRow.Cells(3).HorizontalAlign = HorizontalAlign.Left

            End If
        Catch ex As Exception
            'MsgBox(ex.Message) ' Display any errors.
        End Try
        con.Close()
        con.Dispose()

    End Sub
What I need to do is a calculation on the datetime fields (end - start) and then display this in the "Total Time" column of the GridView.
I have been beating my head against the wall trying to achieve this.
Please and assistance would be greatly appreciated.