Unhandled Exception

Private Sub btnAccept_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAccept.Click
 
        If dgResults.Rows.Count = 0 Then
            MsgBox("cannot accept empty trailer.", MsgBoxStyle.OkOnly)
            Exit Sub
        End If
        'delete contents of tbl_Current_Wave from database.
        Dim oledbConnection As New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;data source='I:\Wave_Selection\Wave_Selection.mdb';Persist Security Info=False")
        oledbConnection.Open()
        Dim oledbCommand As New OleDb.OleDbCommand("DELETE * FROM tbl_Current_Wave", oledbConnection)
        oledbCommand.ExecuteNonQuery()
        oledbConnection.Close()
 
        'get julian date. prompt for trailor name. check if exists.
        Dim x As String
        Dim iCheck As Integer = 0
        'Dim sJulian As String
        'sJulian = Now.DayOfYear.ToString.PadLeft(3, "0")
        x = InputBox("Name the Trailor", "Trailor Name")
        If x = "" Then
            Exit Sub
        End If
 
        Dim stringSQL As String = "SELECT [WAVE] FROM tbl_Waves GROUP BY WAVE "
        Dim zAdapter As New OleDbDataAdapter(stringSQL, connectionString)
        Dim tCheck As New DataTable
        zAdapter.Fill(tCheck)
 
        Dim dview As DataView = tCheck.DefaultView
        For z As Integer = 0 To dview.Table.Rows.Count - 1
            If dview.Table.Rows(z).Item("WAVE") = x Then
                iCheck = iCheck + 1
            End If
        Next z
        If iCheck > 0 Then
            MsgBox("Trailor Name already exists", MsgBoxStyle.Exclamation)
            Exit Sub
        End If
 
        iSkip = iSkip + 1
        'Set datatable equal to the datagridview.
        Dim tSorter1 As New DataTable
        tSorter1.Clear()
        tSorter1 = dgResults.DataSource
 
        'set adapter to tbl_Current_Wave. Store dgResults data in tSorter.
        Me.Validate()
        Dim cn As New OleDbConnection(connectionString)
        cn.Open()
        mAdapter.SelectCommand = New OleDb.OleDbCommand("SELECT * FROM tbl_Current_Wave", New OleDb.OleDbConnection(connectionString))
        Dim cb As New OleDb.OleDbCommandBuilder(mAdapter)
 
        'Add column that will hold wave name
        If Not tSorter1.Columns.Contains("Wave") Then
            Dim WAVE As DataColumn = New DataColumn("WAVE")
            WAVE.DataType = System.Type.GetType("System.String")
            tSorter1.Columns.Add(WAVE)
        End If
 
        'Insert name into wave column
        Dim dv As DataView = tSorter1.DefaultView
        For y As Integer = 0 To dv.Table.Rows.Count - 1
            dv.Table.Rows(y).Item("WAVE") = x
        Next y
 
        'Update Database 
        mAdapter.Update(tSorter1)
        cn.Close()
 
        'clear contents of grid.
        mAdapter.SelectCommand = New OleDb.OleDbCommand("SELECT * FROM tbl_Waves WHERE OAPS = 'Z' ", New OleDb.OleDbConnection(connectionString))
        Dim clearTable As New DataTable
        mAdapter.Fill(clearTable)
        dgResults.DataSource = clearTable
 
        'remove totals from dgvtotal.
        Dim iColumnCount As Integer = 7
        Do Until iColumnCount = 20
            dgvtotal.Item(iColumnCount, 0).Value = ""
            iColumnCount = iColumnCount + 1
        Loop
 
        'Show form with current wave selection
        If F9 Is Nothing OrElse F9.IsDisposed Then
            F9 = New frmVarify
        End If
        F9.Show()
        F9.Activate()
 
    End Sub