Calculated Values in VB ListView Groupings

I am using a ListView to view data from a MySqlDB. 

ListView name is lstMySqlData -- I am able to pull in the data from MySql into the ListView -- then sort into Groups using the Sub code below by calling sub using the following: GroupByEmpNo(lstMySqlData, 1)

See resulting screen shot below:

My question is how to calculate the Claim Diff field by group as shown. The first row of each group would be the time in 100ths since midnight. Each row after that would be the amount of time since the last punch.

Thoughts -- example code -- other

Thanks for your help

Dan

    Public Sub GroupByEmpNo(ByVal lstV As System.Windows.Forms.ListView, ByVal SubItemIndex As Int16)
        Dim flag As Boolean = True
        For Each l As ListViewItem In lstV.Items
            Dim strmyGroupname As String = l.SubItems(SubItemIndex).Text
            For Each lvg As ListViewGroup In lstV.Groups
                If lvg.Name = strmyGroupname Then
                    l.Group = lvg
                    flag = False
                End If
            Next

            Dim BackColor
            BackColor = "FDF5E6"

            For Each g As ListViewGroup In lstV.Groups
                With g
                    For Each i As ListViewItem In .Items
                        i.Font = New Font("Calibri", 10, FontStyle.Bold)
                        i.BackColor = Color.Wheat
                    Next
                End With
            Next
            If flag = True Then
                Dim lstGrp As New ListViewGroup(strmyGroupname, strmyGroupname)
                lstV.Groups.Add(lstGrp)
                l.Group = lstGrp
            End If
            flag = True
        Next
    End Sub

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