隔式跑掉了，這樣應該比較清楚

船名 -------------出港時間 -----------出港港口 ----------入港時間 -----------入港港口
CTPFB0128 --2017/02/28 17:57:00 -------蚵子寮 --------2017/03/01 02:45:00 ---蚵子寮
CTPFB2549 --2017/03/04 00:21:00 -------伽藍 ----------2017/03/04 17:09:00 ---開元
CTPFB2542 --2017/03/05 03:48:00 -------開元 ----------2017/03/05 18:09:00 ---開元
CTPFB2550 --2017/03/04 00:21:00 -------伽藍 ----------2017/03/04 17:09:00 ---開元
CTPFB0199 --2017/02/28 17:57:00 -------蚵子寮 --------2017/03/01 02:45:00 ---蚵子寮
CTPFA0309 --2017/03/04 17:59:04 -------蚵子寮 --------2017/03/04 20:16:35 ---蚵子寮

個人比較喜歡以sql的方式下手，用sql比較容易達成

Imports System.IO
Imports System.Text
Imports System.Data
Public Class Form1

Dim datatableA As New DataTable
Dim datatableB As New DataTable
Dim Namelist As New List(Of String)
Dim NamelistA As New List(Of String)

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim readerA As New IO.StreamReader("D:\AAA.csv", System.Text.Encoding.Default)
Dim lineA As String = ""
Do
lineA = readerA.ReadLine
If lineA Is Nothing Then Exit Do
Namelist.Add(lineA)
Dim columnsA() As String = lineA.Split(",")
Dim newrow As DataRow = datatableA.NewRow
newrow("shipName") = columnsA(0)
newrow("ExitTime") = columnsA(1)
newrow("exitport") = columnsA(2)
newrow("entertime") = columnsA(3)
newrow("enterport") = columnsA(4)
datatableA.Rows.Add(newrow)
Loop
readerA.Close()
DataGridView2.DataSource = datatableA
Me.Text = datatableA.Rows.Count & "rows"
End Sub
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
Dim i As Integer
Dim j As Integer
Dim k As Integer
Dim st As String = ""
Dim sy As String = ""
i = Namelist.Count
For j = 0 To i - 1
st = Namelist.Item(j).Substring(10, Len(Namelist.Item(j)) - 10)
For k = j + 1 To i - 1
sy = Namelist.Item(k).Substring(10, Len(Namelist.Item(k)) - 10)
If st = sy Then
NamelistA.Add(Namelist.Item(j))
End If
Next
Next
For Each AAA In NamelistA
Dim columnsB() As String = AAA.Split(",")
Dim nrow As DataRow = datatableB.NewRow
nrow("shipName") = columnsB(0)
nrow("ExitTime") = columnsB(1)
nrow("exitport") = columnsB(2)
nrow("entertime") = columnsB(3)
nrow("enterport") = columnsB(4)
datatableB.Rows.Add(nrow)
Next
DataGridView3.DataSource = datatableB

End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load

datatableA.Columns.Add("ShipName")
datatableA.Columns.Add("ExitTime")
datatableA.Columns.Add("ExitPort")
datatableA.Columns.Add("EnterTime")
datatableA.Columns.Add("EnterPort")

datatableB.Columns.Add("ShipName")
datatableB.Columns.Add("ExitTime")
datatableB.Columns.Add("ExitPort")
datatableB.Columns.Add("EnterTime")
datatableB.Columns.Add("EnterPort")

End Sub
End Class