how to generate ID based on comboboxes selection

[pandeysk_13]

    **hello all,
    i am creating a programme for my institute which helps in their administrative process.
    i am using visual studio(basic) 2010.
    which is connected with ms access database (abcdata.accdb)
    the database is having table called session with columns sessionID,sessioncode,sessionname.

    * sessionID data = 1,2,3,4
    * sessioncode data = 13,14,15,16
    * sessionname data = 2013,2014,2015,2016

    the another is having table called course with a columns courseID, coursecode, coursename

    * courseID data = 1,2,3,4
    * coursecode data = 01,02,03,04
    * coursename data = ba,ma,bsc.msc

    the other table called courseyear with colums courseyearID, courseyearcode, courseyearname.

    * courseyearID = 1,2,3,4
    * courseyearcode = 01,02,03,04
    * courseyearname = I,II,II,IV

    in vb a form is having 3 comboboxes and one textbox.
    i am pulling data from database to my comboboxes with this code:**

**Private Sub loadcourse()**
    Dim OleDBC As New OleDbCommand
    Dim OleDBDR As OleDbDataReader
    With OleDBC
        .Connection = conn
        .CommandText = "SELECT coursename FROM tblcourse"
    End With
    OleDBDR = OleDBC.ExecuteReader
    cmbcourse.Items.Clear()

    If OleDBDR.HasRows Then
        While OleDBDR.Read
            cmbcourse.Items.Add(OleDBDR.Item(0))

        End While
    End If
End Sub
**Private Sub loadcourseyear()**
    Dim OleDBC As New OleDbCommand
    Dim OleDBDR As OleDbDataReader
    With OleDBC
        .Connection = conn
        .CommandText = "SELECT courseyearname FROM tblcourseyear"
    End With
    OleDBDR = OleDBC.ExecuteReader
    cmbcourseyear.Items.Clear()

    If OleDBDR.HasRows Then
        While OleDBDR.Read
            cmbcourseyear.Items.Add(OleDBDR.Item(0))

        End While
    End If
End Sub
* loadsession(in the same manner)
  **now i just want to create a unique ID based on comboboxes selection like this:**

*   if cmbsession.select = 2013
*   and if cmbcourse.select = ba
*   and if cmbcourseyear.select = II

then the textbox named txtrollnumber must fill like this: **130102**
**i tried with this code but it is showing number like this : 010213**
Private Sub cmbcourseyear_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbcourseyear.SelectedIndexChanged
    Try
        ' Open connection

        Dim sqlQRY As String = "select * from tblcourseyear where courseyearname='" + cmbcourseyear.Text + "'"
        'create data adapter
        Dim da As OleDbDataAdapter = New OleDbDataAdapter(sqlQRY, conn)
        'create dataset
        Dim ds As DataSet = New DataSet
        'fill dataset
        da.Fill(ds, "tblcourseyear")
        'get data table
        Dim dt As DataTable = ds.Tables("tblcourseyear")
        'display data
        Dim row As DataRow
        For Each row In dt.Rows
            txtrollnumber.Text = row("courseyearcode") + txtrollnumber.Text

        Next row
        If ds.Tables("tblcourseyear").Rows.Count = 0 Then
            MessageBox.Show("Sorry No Record Found Please Try Again!", " You Software name ", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End If
        ' Close connection
        conn.Close()
    Catch ex As OleDbException
        MessageBox.Show("Customer Not found" + ex.Message)
    End Try

End Sub     
with this i also want to add a number after 130102 like this : 0001,0002,0003,0004 and so on....... this number must genetate on the basis of the IDs saved in the datable i.e.if 1301020001 is exist in datatable row then the last 4 digets must change with 0002.and in i select **130201**
if 1302010001 or last highest number from last 4 match with first 6 degits is exist than the number must change to +1 on last 4 degits.
****i tried with this code which i got from your fourm but is is generating code at form load event.**
Private Function GenerateID() As String
    Dim value As String = "00000"
    Dim studentID As String
    Try
        ' Fetch the latest ID from the database
        con.Open()
        mycmd = New OleDbCommand("SELECT TOP 1 studentID FROM tblstudentsregistration ORDER BY studentID DESC", Con)
        mydr = mycmd.ExecuteReader(CommandBehavior.CloseConnection)
        If mydr.HasRows Then
            mydr.Read()
            value = mydr.Item("studentID")
        End If
        mydr.Close()
        'Increase the ID by 1
        value += 1
        ' Because incrementing a string with an integer removes 0's
        ' we need to replace them. If necessary.
        If value <= 9 Then 'Value is between 0 and 10
            value = "00000" & value
        ElseIf value <= 99 Then 'Value is between 9 and 100
            value = "0000" & value
        ElseIf value <= 999 Then 'Value is between 999 and 1000
            value = "000" & value
        End If
    Catch ex As Exception
        ' If an error occurs, check the connection state and close it if necessary.
        If con.State = ConnectionState.Open Then
            con.Close()
        End If
        value = "00000"
    End Try
    Return value
End Function

other then this u can see i want this because i am trying to create a database which must save the students data year wise, so that whenever we need to know a detail any students then we can find with query.
sorry if not explaned in better way because i am very new in this
please help me
thanks in advance

[poojavb]

Could u tell the format how u should get 130102 ???
Still confused with ur requirement....

[pandeysk_13]

hello,
thanks for response. as you can see i create a combobox_SelectedIndexChanged.
same as this i have create an event for all comboboxes which display 100113 but i am not confrim that it is true.
please help me...