How to compare current value with previous in loop using datatable

See more:

VB9

VB

Hi this is my code. I need to go through the for loop to get the value from a datatable for each row and compare the value. Example the datatable out put is
total Percentage

1192 0.8
1964 0.3
1964 0.1

So it should compare 0.8 minus with 0.3. If the reminder greater than 0.3 Then it should be minus again with the 0.3. So the bal is 0.5 minus 0.3. So how actually do it in a loop.

For Each TesterShutdown As DataRow In tblRawTesterShutdown.Rows
                            For Each ShutdownCriteria As DataRow In tblShutdownCriteria.Rows
                                If TesterShutdown.Item("E_FIELD") = ShutdownCriteria.Item("E_CODE") _
                                And TesterShutdown.Item("F_FIELD") = ShutdownCriteria.Item("F_CODE") _
                                And TesterShutdown.Item("G_FIELD") = ShutdownCriteria.Item("G_CODE") _
                                And TesterShutdown.Item("FAMILY") = ShutdownCriteria.Item("FAMILY") Then
                                    If tblRawTesterShutdown.Rows.Count > 1 Then

                                        Dim FirstPer As Double = 0
                                        Dim SecPer As Double = tblRawTesterShutdown.Rows(1).Item("PERCENTAGE")
                                        Dim BalPer As Double = 0.0

                                        <big>For c As Integer = 0 To tblRawTesterShutdown.Rows.Count - 1
                                   
                                          
                                        Next</big>
                                    End If
                                End If
                            Next
                            Exit For
                        Next

Thanks in advance.Need it urgently.Thanks again